drm/amd/display: Remove unnecessary warning

[why]
The warning message floods the dmesg log on Tonga even
though it is expected to have a pix_clk set to zero,
when the pipe is not active.
[how]
remove the assert
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce100/dce100_hw_sequencer.c

@@ -149,10 +149,6 @@ static uint32_t get_max_pixel_clock_for_all_paths(
 			max_pix_clk =
 				pipe_ctx->stream_res.pix_clk_params.requested_pix_clk;
 	}
-
-	if (max_pix_clk == 0)
-		ASSERT(0);
-
 	return max_pix_clk;
 }