drm/amd/display: Fix unused variable ‘should_lock_all_pipes’

Fix below compilation error:

drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:3524:7: error: unused variable 'should_lock_all_pipes' [-Werror,-Wunused-variable]
        bool should_lock_all_pipes = (update_type != UPDATE_TYPE_FAST);

Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc.c

@@ -3521,7 +3521,6 @@ static void commit_planes_for_stream_fast(struct dc *dc,
 {
 	int i, j;
 	struct pipe_ctx *top_pipe_to_program = NULL;
-	bool should_lock_all_pipes = (update_type != UPDATE_TYPE_FAST);
 	dc_z10_restore(dc);
 
 	for (j = 0; j < dc->res_pool->pipe_count; j++) {