wifi: ath12k: Make QMI message rules const

Commit ff6d3658

 ("soc: qcom: qmi: use const for struct
qmi_elem_info") allows QMI message encoding/decoding rules
to be const, so do that for ath12k.

Compile tested only.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20231217-ath12k-qmi_elem_info-const-v1-1-7ebb0de0a2b6@quicinc.com