drm/amd/display: remove set but not used variable 'core_freesync'

Fixes gcc '-Wunused-but-set-variable' warning:

rivers/gpu/drm/amd/amdgpu/../display/modules/freesync/freesync.c:
 In function mod_freesync_get_settings:
drivers/gpu/drm/amd/amdgpu/../display/modules/freesync/freesync.c:984:24:
 warning: variable core_freesync set but not used [-Wunused-but-set-variable]

It is not used since commit 98e6436d ("drm/amd/display: Refactor FreeSync module")
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/modules/freesync/freesync.c

@@ -981,13 +981,9 @@ void mod_freesync_get_settings(struct mod_freesync *mod_freesync,
 		unsigned int *inserted_frames,
 		unsigned int *inserted_duration_in_us)
 {
-	struct core_freesync *core_freesync = NULL;
-
 	if (mod_freesync == NULL)
 		return;
 
-	core_freesync = MOD_FREESYNC_TO_CORE(mod_freesync);
-
 	if (vrr->supported) {
 		*v_total_min = vrr->adjust.v_total_min;
 		*v_total_max = vrr->adjust.v_total_max;