wifi: ath11k: Fix qmi_msg_handler data structure initialization

qmi_msg_handler is required to be null terminated by QMI module.
There might be a case where a handler for a msg id is not present in the
handlers array which can lead to infinite loop while searching the handler
and therefore out of bound access in qmi_invoke_handler().
Hence update the initialization in qmi_msg_handler data structure.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.5.0.1-01100-QCAHKSWPL_SILICONZ-1

Signed-off-by: Rahul Bhattacharjee <quic_rbhattac@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20221021090126.28626-1-quic_rbhattac@quicinc.com