wifi: rtw88: Lock rtwdev->mutex before setting the LED

wifi: rtw88: Lock rtwdev->mutex before setting the LED

Some users report that the LED blinking breaks AP mode somehow. Most
likely the LED code and the dynamic mechanism are trying to access the
hardware registers at the same time. Fix it by locking rtwdev->mutex
before setting the LED and unlocking it after.

Fixes: 4b6652bc6d8d ("wifi: rtw88: Add support for LED blinking")
Closes: https://github.com/lwfinger/rtw88/issues/305
Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/ed69fa07-8678-4a40-af44-65e7b1862197@gmail.com