drm/amdgpu: rework amdgpu_userq_wait_ioctl v4

drm/amdgpu: rework amdgpu_userq_wait_ioctl v4

Lockdep was complaining about a number of issues here. Especially lock
inversion between syncobj, dma_resv and copying things into userspace.

Rework the functionality. Split it up into multiple functions,
consistenly use memdup_array_user(), fix the lock inversions and a few
more bugs in error handling.

v2: drop the dma_fence leak fix, turned out that was actually correct,
    just not well documented. Apply some more cleanup suggestion from
    Tvrtko.
v3: rebase on already done cleanups
v4: add missing dma_fence_put() in error path.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Sunil Khatri <sunil.khatri@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>