drm/amd/display: Fix use of uninitialized union

[Why]
An uninitialized variable would randomly initialize to a large
value. This caused enough delay to fail DP Compliance Test 400.2.1.

[How]
Initialize the variable.

Signed-off-by: John Barberiz <John.Barberiz@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@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/core/dc_link_dp.c

@@ -47,7 +47,7 @@ static void wait_for_training_aux_rd_interval(
 	struct dc_link *link,
 	uint32_t default_wait_in_micro_secs)
 {
-	union training_aux_rd_interval training_rd_interval;
+	union training_aux_rd_interval training_rd_interval = {0};
 
 	/* overwrite the delay if rev > 1.1*/
 	if (link->dpcd_caps.dpcd_rev.raw >= DPCD_REV_12) {