drm/amdgpu: fix and cleanup gmc_v8_0_flush_gpu_tlb_pasid

Testing for reset is pointless since the reset can start right after the
test. Grab the reset semaphore instead.

The same PASID can be used by more than once VMID, build a mask of VMIDs
to invalidate instead of just restting the first one.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Shashank Sharma <shashank.sharma@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>