media: marvel-ccic: allow ccic and mmp drivers to coexist

Randconfig builds fail when one of the two is a built-in driver and
the other one is a loadable module:

drivers/media/platform/marvell-ccic/mcam-core.o: In function `mccic_register':
mcam-core.c:(.text+0x2594): undefined reference to `__this_module'
drivers/media/platform/marvell-ccic/mcam-core.o:(.rodata+0x50): undefined reference to `__this_module'

The problem is that mcam-core.c can not be built both ways at the smae
time. However, we can make kbuild take care of that by making the core
driver a separate module, which can be either built-in or loadable
as needed.
Making it a separate module requires exporting a few symbols and
adding the module license from the header.

Fixes: 0a9c643c

 ("media: marvel-ccic: re-enable mmp-driver build")

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>