drm/amdgpu: csa unmap use uninterruptible lock

After process exit to unmap csa and free GPU vm, if signal is accepted
and then waiting to take vm lock is interrupted and return, it causes
memory leaking and below warning backtrace.

Change to use uninterruptible wait lock fix the issue.

WARNING: CPU: 69 PID: 167800 at amd/amdgpu/amdgpu_kms.c:1525
 amdgpu_driver_postclose_kms+0x294/0x2a0 [amdgpu]
 Call Trace:
  <TASK>
  drm_file_free.part.0+0x1da/0x230 [drm]
  drm_close_helper.isra.0+0x65/0x70 [drm]
  drm_release+0x6a/0x120 [drm]
  amdgpu_drm_release+0x51/0x60 [amdgpu]
  __fput+0x9f/0x280
  ____fput+0xe/0x20
  task_work_run+0x67/0xa0
  do_exit+0x217/0x3c0
  do_group_exit+0x3b/0xb0
  get_signal+0x14a/0x8d0
  arch_do_signal_or_restart+0xde/0x100
  exit_to_user_mode_loop+0xc1/0x1a0
  exit_to_user_mode_prepare+0xf4/0x100
  syscall_exit_to_user_mode+0x17/0x40
  do_syscall_64+0x69/0xc0

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7dbbfb3c)
Cc: stable@vger.kernel.org