net: ipa: 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 IPA.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Reviewed-by: Sibi Sankar <quic_sibis@quicinc.com>
Signed-off-by: David S. Miller <davem@davemloft.net>