drm/amd/amdgpu: fix comparison pointer to bool warning in gfx_v10_0.c

Fixes coccicheck warning:

drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c:3563:5-31: WARNING: Comparison to bool
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c

@@ -3560,7 +3560,7 @@ static void gfx_v10_0_check_fw_write_wait(struct amdgpu_device *adev)
 		break;
 	}
 
-	if (adev->gfx.cp_fw_write_wait == false)
+	if (!adev->gfx.cp_fw_write_wait)
 		DRM_WARN_ONCE("CP firmware version too old, please update!");
 }