ath11k: unlock mutex during failure in qmi fw ready

qmi firmware ready event start to initialize the core modules and
the sequence executed with mutex lock. In case of any failure
mutex should be unlocked otherwise it will hang during the recovery.

Signed-off-by: Govindaraj Saminathan <gsamin@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>