UPSTREAM: media: ipu6: optimize the IPU6 MMU unmapping flow

The MMU mapping flow is optimized for improve the performance, the
unmapping flow could also be optimized to follow same flow.

Signed-off-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>

(cherry picked from commit 1faf84ff)

Bug: 394358942
Change-Id: If01b5ef2815b6d861ba2074b075bf83afbef3652
Signed-off-by: Ricardo Ribalda <ribalda@google.com>