drm/amdgpu/userq: amdgpu_userq_vm_validate does not need userq mutex

drm/amdgpu/userq: amdgpu_userq_vm_validate does not need userq mutex

amdgpu_userq_vm_validate function does not need userq_mutex and exec
lock is good enough to locking all bos and updating the eviction fence.

Also since we only need userq_mutex for amdgpu_userq_restore_all
so move the locks in the function itself.

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