Change LED state reader to consume vents, as soon as "gadget state connected to host" could be determined about p4wnp1_aloa HOT 2 CLOSED

while $true; do cat /sys/kernel/debug/20980000.usb/regdump | grep HPRT0; sleep 1; done

Host Port Control and Status register
=====================================
Reg value is dumpable via debugfs for DesignWare USB 2.0 host controller (dwc2)
The dump could be triggered via debugff by reading `/sys/kernel/debug/20980000.usb/regdump` which holds the value for the register in `HPRT0`.
The problem with the approach: The register dump has to be triggered by polling /sys/kernel/debug/20980000.usb/regdump and dumps ALL registers.
This seems to crash the UDC from time to time, in contrast to the comment of the kernel source (https://github.com/raspberrypi/linux/blob/rpi-4.14.y/drivers/usb/dwc2/debugfs.c#L402).

HPRT --> Host Port Control and Status Register, details on data struct:
https://www.cl.cam.ac.uk/~atm26/ephemeral/rpi/dwc_otg/doc/html/unionhprt0__data.html#a964274b5d22e89ca4490f66dff3c763


Meanings of struct fields:
https://www.intel.com/content/www/us/en/programmable/documentation/sfo1410144425160/sfo1410067646785/sfo1410069362932/sfo1410069623936/sfo1410069628257/sfo1410069409998.html

01741 typedef union hprt0_data {
01743         uint32_t d32;
01745         struct {
01746                 unsigned prtconnsts:1;
01747                 unsigned prtconndet:1;
01748                 unsigned prtena:1;
01749                 unsigned prtenchng:1;

01750                 unsigned prtovrcurract:1;
01751                 unsigned prtovrcurrchng:1;
01752                 unsigned prtres:1;
01753                 unsigned prtsusp:1;

01754                 unsigned prtrst:1;
01755                 unsigned reserved9:1;
01756                 unsigned prtlnsts:2;

01757                 unsigned prtpwr:1;
01758                 unsigned prttstctl:4;
01759                 unsigned prtspd:2;
01760 #define DWC_HPRT0_PRTSPD_HIGH_SPEED 0
01761 #define DWC_HPRT0_PRTSPD_FULL_SPEED 1
01762 #define DWC_HPRT0_PRTSPD_LOW_SPEED      2
01763                 unsigned reserved19_31:13;
01764         } b;
01765 } hprt0_data_t;

Test results (polling /sys/kernel/debug/20980000.usb/regdump and parsing "HPRT0")
=================================================================================

USB gadget running, but OTG adapter attached, NO device connected to the OTG adapter
--> prtlnsts = 0 (No data line on positive logic level)
--> prtpwr = 1 (the port is powered ... at least if there's no overcorrency)
--> prtconnsts = 0 (No device attached)

USB gadget running, but OTG adapter attached, device connected to the OTG adapter
--> prtlnsts = 0,1 or 2 (changes)
--> prtpwr = 1 (the port is powered ... at least if there's no overcorrency)
--> prtconnsts = 1 (A device is attached)
--> prtspd = 1 or 2 (for non high speed devices)

USB gadget running, no OTG adapter attached, but NOT connected to host as a peripheral
--> prtlnsts = 1 (Logic Level of D+ is 1, logic level of D- is 0)
--> prtpwr = 0
--> prtconnsts = 0 (No device attached)

USB gadget running, no OTG adapter attached, connected to host as a peripheral
--> prtlnsts = 0 (both, D+ and D-, are indicated as low)
--> prtpwr = 0
--> prtconnsts = 0 (No device attached)
--> in fact the whole HPRT0 is set to 0x00000000 if connected to a host in device mode