drm/amdgpu/display: drop set but unused variable

No longer used so drop it.

Fixes: ec457f83 ("drm/amd/display: Drop unnecessary detect link code")
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1022,7 +1022,6 @@ static bool detect_link_and_local_sink(struct dc_link *link,
 	struct dc_sink *prev_sink = NULL;
 	struct dpcd_caps prev_dpcd_caps;
 	enum dc_connection_type new_connection_type = dc_connection_none;
-	enum dc_connection_type pre_connection_type = dc_connection_none;
 	const uint32_t post_oui_delay = 30; // 30ms
 
 	DC_LOGGER_INIT(link->ctx->logger);
@@ -1059,7 +1058,6 @@ static bool detect_link_and_local_sink(struct dc_link *link,
 
 	link_disconnect_sink(link);
 	if (new_connection_type != dc_connection_none) {
-		pre_connection_type = link->type;
 		link->type = new_connection_type;
 		link->link_state_valid = false;