staging: vc04_services: vchiq_mmal: Rename service_callback()

Rename the service_callback static function to mmal_service_callback()
since the function signature conflicts with:

extern int
service_callback(struct vchiq_instance *vchiq_instance, enum vchiq_reason reason,
struct vchiq_header *header, unsigned int handle, void *bulk_userdata);

in vc04_services/interface/vchiq_arm/vchiq_arm.h

In a subsequent patch, we will include vchiq_arm.h header to
mmal-vchiq.c, which will then complain of this conflict. Hence,
this patch is meant to handle the conflict beforehand.

Reviewed-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Umang Jain <[e-mail]>
Reviewed-by: Stefan Wahren <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c

···
 }
 
 /* incoming event service callback */
-static int service_callback(struct vchiq_instance *vchiq_instance,
-			    enum vchiq_reason reason, struct vchiq_header *header,
-			    unsigned int handle, void *bulk_ctx)
+static int mmal_service_callback(struct vchiq_instance *vchiq_instance,
+				 enum vchiq_reason reason, struct vchiq_header *header,
+				 unsigned int handle, void *bulk_ctx)
 {
 	struct vchiq_mmal_instance *instance = vchiq_get_service_userdata(vchiq_instance, handle);
 	u32 msg_len;
···
 		.version		= VC_MMAL_VER,
 		.version_min		= VC_MMAL_MIN_VER,
 		.fourcc			= VCHIQ_MAKE_FOURCC('m', 'm', 'a', 'l'),
-		.callback		= service_callback,
+		.callback		= mmal_service_callback,
 		.userdata		= NULL,
 	};