drm/amd/display: Increase DPCD read retries

[Why]
Empirical measurement of some monitors that fail to read EDID while
booting shows that the number of retries with a 30ms delay between
tries is as high as 16.

[How]
Increase number of retries to 20.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4672
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit ad1c59a)
Cc: stable@vger.kernel.org

Author: superm1

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c

@@ -1691,7 +1691,7 @@ static bool retrieve_link_cap(struct dc_link *link)
 	union edp_configuration_cap edp_config_cap;
 	union dp_downstream_port_present ds_port = { 0 };
 	enum dc_status status = DC_ERROR_UNEXPECTED;
-	uint32_t read_dpcd_retry_cnt = 3;
+	uint32_t read_dpcd_retry_cnt = 20;
 	int i;
 	struct dp_sink_hw_fw_revision dp_hw_fw_revision;
 	const uint32_t post_oui_delay = 30; // 30ms