drm/amd/display: remove useless check in should_enable_fbc()

It does not make sense to compare a pointer to array element with NULL.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 65d38262 ("drm/amd/display: fbc state could not reach while enable fbc")
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Dembskiy Igor <dii@itb.spb.ru>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c

@@ -1997,9 +1997,6 @@ static bool should_enable_fbc(struct dc *dc,
 
 			pipe_ctx = &res_ctx->pipe_ctx[i];
 
-			if (!pipe_ctx)
-				continue;
-
 			/* fbc not applicable on underlay pipe */
 			if (pipe_ctx->pipe_idx != underlay_idx) {
 				*pipe_idx = i;