freedreno/drm: sync uapi again

"pad" was missing in Mesa's msm_drm.h. sizeof(drm_msm_gem_info) remains the same, but now the compiler initializes the field to zero.

Buffer allocation results in EINVAL without this for me.

Cc: Rob Clark robdclark@gmail.com Cc: Kristian Høgsberg hoegsberg@gmail.com Signed-off-by: Chia-I Wu olvaffe@gmail.com Reviewed-by: Kristian H. Kristensen hoegsberg@gmail.com