drm/amdgpu: Fix masking binary not operator on two mask operations

Currently the ! operator is incorrectly being used to flip bits on
mask values. Fix this by using the bit-wise ~ operator instead.

Addresses-Coverity: ("Logical vs. bitwise operator")
Fixes: 3c9a7b7d ("drm/amdgpu: update mmhub mgcg&ls for mmhub_v2_3")
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>