ath10k: add testmode

Add testmode interface for starting and using UTF firmware which is used to run
factory tests. This is implemented by adding new state ATH10K_STATE_UTF and user
space can enable this state with ATH10K_TM_CMD_UTF_START command. To go back to
normal mode user space can send ATH10K_TM_CMD_UTF_STOP.

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: support firmware crash-by-assert

10.1 firmware does not have an official way to
cause assert on purpose, but it can be done with
carefully crafted WMI command.  This is a different
kind of crash from the 'hard' crash, which is
a bad memory dereference.

Different crashes decode in different manners, so
this will help the crash-report testing as well as
offer better ways to test firmware failure and
recovery.

kvalo: move the wmi command creation to debug.c, modify
the info print

Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: fix debugfs_create_dir() checking

The function may return an -ENODEV if debugfs is
disabled in kernel. This should originally be
guarded by ath10k's Kconfig but it still makes
sense to check for the non-NULL errno return
value.

Reported-by: Matteo Croce <matteo@openwrt.org>
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>