fix the gpio pin for ar9287-based usb devices

[Kevin Lo]

Hi,

AR9287-based usb devices use GPIO pin 10 for LED, not 8.
Tested with TP-LINK TL-WN821N V3.  ok?

Index: sys/dev/ic/ar9287.c
===================================================================
RCS file: /cvs/src/sys/dev/ic/ar9287.c,v
retrieving revision 1.27
diff -u -p -u -p -r1.27 ar9287.c
--- sys/dev/ic/ar9287.c 29 Mar 2019 11:04:40 -0000      1.27
+++ sys/dev/ic/ar9287.c 31 Mar 2019 10:12:22 -0000
@@ -104,7 +104,7 @@ ar9287_attach(struct athn_softc *sc)
            AR9287_HTC_EEP_START_LOC : AR9287_EEP_START_LOC;
        sc->eep_size = sizeof(struct ar9287_eeprom);
        sc->ngpiopins = (sc->flags & ATHN_FLAG_USB) ? 16 : 11;
-       sc->led_pin = 8;
+       sc->led_pin = (sc->flags & ATHN_FLAG_USB) ? 10 : 8;
        sc->workaround = AR9285_WA_DEFAULT;
        sc->ops.setup = ar9287_setup;
        sc->ops.swap_rom = ar9287_swap_rom;