drm/msm: Add support for pointer params

The 64b value field is already suffient to hold a pointer instead of
immediate, but we also need a length field.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20220317165144.222101-2-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>

include/uapi/drm/msm_drm.h

@@ -95,6 +95,8 @@ struct drm_msm_param {
 	__u32 pipe;           /* in, MSM_PIPE_x */
 	__u32 param;          /* in, MSM_PARAM_x */
 	__u64 value;          /* out (get_param) or in (set_param) */
+	__u32 len;            /* zero for non-pointer params */
+	__u32 pad;            /* must be zero */
 };
 
 /*