drm: mali-dp: remove unused variable

drm: mali-dp: remove unused variable

The newly introduced function causes a harmless build warning:

drivers/gpu/drm/arm/malidp_planes.c: In function 'malidp_plane_atomic_print_state':
drivers/gpu/drm/arm/malidp_planes.c:98:23: error: unused variable 'mp' [-Werror=unused-variable]

The variable serves no purpose here and can be removed.

Fixes: 242f43b69c61 ("drm: mali-dp: add atomic_print_state for planes")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>