drm/amdgpu: Move null pointer dereference check

Null pointer dereference check should have been checked,
ahead of below routine.
	struct amdgpu_device *adev = hwmgr->adev;

With this commit, it could avoid potential NULL dereference.

Signed-off-by: Austin Kim <austindh.kim@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/powerplay/smumgr/smu8_smumgr.c

@@ -722,16 +722,17 @@ static int smu8_request_smu_load_fw(struct pp_hwmgr *hwmgr)
 
 static int smu8_start_smu(struct pp_hwmgr *hwmgr)
 {
-	struct amdgpu_device *adev = hwmgr->adev;
+	struct amdgpu_device *adev;
 
 	uint32_t index = SMN_MP1_SRAM_START_ADDR +
 			 SMU8_FIRMWARE_HEADER_LOCATION +
 			 offsetof(struct SMU8_Firmware_Header, Version);
 
-
 	if (hwmgr == NULL || hwmgr->device == NULL)
 		return -EINVAL;
 
+	adev = hwmgr->adev;
+
 	cgs_write_register(hwmgr->device, mmMP0PUB_IND_INDEX, index);
 	hwmgr->smu_version = cgs_read_register(hwmgr->device, mmMP0PUB_IND_DATA);
 	pr_info("smu version %02d.%02d.%02d\n",