media: ipu6: move the l2_unmap() up before l2_map()

l2_map() and l2_unmap() are better to be grouped together.
l2_unmap() will soon be called from l2_map() for mapping
optimization.

Signed-off-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Jianhui Dai <jianhui.j.dai@intel.com>
[Sakari Ailus: Rebase on debug print fixes on 32-bit.]
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>