accel/ivpu: Fix dev open/close races with unbind

  - Add context_list_lock to synchronize user context addition/removal
  - Use drm_dev_enter() to prevent unbinding the device during ivpu_open()
    and vpu address allocation

Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Reviewed-by: Wachowski, Karol <karol.wachowski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240122120945.1150728-2-jacek.lawrynowicz@linux.intel.com