We need to hold vm->lock before the xe_vm_is_closed_or_banned().

Else we get this splat:
[  802.555227] ------------[ cut here ]------------
[  802.555234] WARNING: CPU: 33 PID: 3122 at drivers/gpu/drm/xe/xe_vm.h:60
[  802.555515] CPU: 33 PID: 3122 Comm: xe_exec_fault_m Tainted:
...
[  802.555709] Call Trace:
[  802.555714]  <TASK>
[  802.555720]  ? __warn+0x81/0x170
[  802.555737]  ? xe_vm_madvise_ioctl+0x2de/0x440 [xe]

Fixes: 9d858b69 ("drm/xe: Ban a VM if rebind worker hits an error")
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Brian Welty <brian.welty@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>