media: atmel: atmel-isc-base: fix enum calls default format

With some sensors, the mbus code must match the one that sensor supports.
In this case we should initialize the mbus_code of the fse/fie before
calling the subdev, and not after.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>