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>