media: atmel: atmel-isc: split driver into driver base and isc

This splits the Atmel ISC driver into a common base: atmel-isc-base.c
and the driver probe/dt part , atmel-sama5d2-isc.c
This is needed to keep a common ground for the sensor controller which will
be reused.
The atmel-isc will use the common symbols inside the atmel-isc-base
Future driver will also use the same symbols and redefine different aspects,
for a different version of the ISC.
This is done to avoid complete code duplication by creating a totally
different driver for the new variant of the ISC.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil-cisco@xs4all.nl: folded 'atmel: atmel-sama5d2-isc: fixed checkpatch warnings' into this patch]
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>