mhi: unconstify mhi_event_config

Some parameters may have to be determined at runtime.
It is the case for the event ring MSI vector.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

include/linux/mhi.h

@@ -279,7 +279,7 @@ struct mhi_controller_config {
 	u32 num_channels;
 	const struct mhi_channel_config *ch_cfg;
 	u32 num_events;
-	const struct mhi_event_config *event_cfg;
+	struct mhi_event_config *event_cfg;
 	bool use_bounce_buf;
 	bool m2_no_db;
 };