wifi: ath12k: Fix locking in "QMI firmware ready" error paths

wifi: ath12k: Fix locking in "QMI firmware ready" error paths

If ag->mutex has been locked, unlock it before returning. If it has not
been locked, do not unlock it before returning. These bugs have been
detected by the Clang thread-safety analyzer.

Cc: Karthikeyan Periyasamy <quic_periyasa@quicinc.com>
Cc: Jeff Johnson <jeff.johnson@oss.qualcomm.com>
Fixes: ee146e11b4d9 ("wifi: ath12k: refactor core start based on hardware group")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Aditya Kumar Singh <aditya.kumar.singh@oss.qualcomm.com>
Link: https://patch.msgid.link/20250206221317.3845663-1-bvanassche@acm.org
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>