drm/amdgpu/psp: use define rather than magic number for mode1 reset

Use the define rather than hardcoded value.
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/psp_v3_1.c

@@ -590,7 +590,7 @@ static int psp_v3_1_mode1_reset(struct psp_context *psp)
 	}
 
 	/*send the mode 1 reset command*/
-	WREG32(offset, 0x70000);
+	WREG32(offset, GFX_CTRL_CMD_ID_MODE1_RST);
 
 	mdelay(1000);