media: radio: allow building ISA drivers with COMPILE_TEST

Several radio devices only build on i386, because they depend
on ISA. Allow them to build on other archs by adding a
COMPILE_TEST check.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>