media: omap3isp: Allow it to build with COMPILE_TEST

There aren't much things required for it to build with COMPILE_TEST.
It just needs to not compile the code that depends on arm-specific
iommu implementation.

Co-developed-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>