drm/amd/display: Initialize lt_settings on instantiation

[WHY]
lt_settings' pointers remain uninitialized but nonzero if display fails
to light up with no DPCD/EDID info populated, leading to a hang on access

Reviewed-by: Nicholas Kazlauskas <[e-mail]>
Acked-by: Alan Liu <[e-mail]>
Signed-off-by: Michael Strauss <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/core/dc_link_dpia.c

···
 	bool skip_video_pattern)
 {
 	enum link_training_result result;
-	struct link_training_settings lt_settings;
+	struct link_training_settings lt_settings = {0};
 	uint8_t repeater_cnt = 0; /* Number of hops/repeaters in display path. */
 	int8_t repeater_id; /* Current hop. */