drm/amd/display: Remove OTG DIV register write for Virtual signals.

[ Upstream commit 709671f ]

[WHY]
Hot plugging and then hot unplugging leads to k1 and k2 values to
change, as signal is detected as a virtual signal on hot unplug. Writing
these values to OTG_PIXEL_RATE_DIV register might cause primary display
to blank (known hw bug).

[HOW]
No longer write k1 and k2 values to register if signal is virtual, we
have safe guards in place in the case that k1 and k2 is unassigned so
that an unknown value is not written to the register either.

Cc: stable@vger.kernel.org
Cc: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Samson Tam <Samson.Tam@amd.com>
Reviewed-by: Alvin Lee <Alvin.Lee2@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Saaem Rizvi <SyedSaaem.Rizvi@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Saaem Rizvi

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_hwseq.c

@@ -1180,7 +1180,7 @@ unsigned int dcn32_calculate_dccg_k1_k2_values(struct pipe_ctx *pipe_ctx, unsign
 			*k2_div = PIXEL_RATE_DIV_BY_2;
 		else
 			*k2_div = PIXEL_RATE_DIV_BY_4;
-	} else if (dc_is_dp_signal(stream->signal) || dc_is_virtual_signal(stream->signal)) {
+	} else if (dc_is_dp_signal(stream->signal)) {
 		if (two_pix_per_container) {
 			*k1_div = PIXEL_RATE_DIV_BY_1;
 			*k2_div = PIXEL_RATE_DIV_BY_2;