drm/amdgpu/swsmu: fix error return code of smu_v11_0_set_allowed_mask()

When bitmap_empty() or feature->feature_num triggers an error,
no error return code of smu_v11_0_set_allowed_mask() is assigned.
To fix this bug, ret is assigned with -EINVAL as error return code.

Reviewed-by: Evan Quan <evan.quan@amd.com>
Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>