drm/amdgpu/soc15: drop dead function

Maybe a leftover from bringup?
Reviewed-by: NChunming Zhou <david1.zhou@amd.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/soc15.c

@@ -566,13 +566,6 @@ static uint32_t soc15_get_rev_id(struct amdgpu_device *adev)
 		return nbio_v6_1_get_rev_id(adev);
 }
 
-
-int gmc_v9_0_mc_wait_for_idle(struct amdgpu_device *adev)
-{
-	/* to be implemented in MC IP*/
-	return 0;
-}
-
 static const struct amdgpu_asic_funcs soc15_asic_funcs =
 {
 	.read_disabled_bios = &soc15_read_disabled_bios,