wifi: ath11k: constify MHI channel and controller configs

Unlike the event configuration which can be modified by MHI, the
channel and controller configurations are expected to be const. And
since they are not modified locally, constify them to prevent runtime
modification.

No functional changes, 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/20240223-mhi-const-wifi-ath11k-v1-1-51b9d42d2639@quicinc.com