wifi: ath11k: 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 ath11k.

Compile tested only.
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220915002303.12206-1-quic_jjohnson@quicinc.com