media: sound, media: allow building ISA drivers it with COMPILE_TEST

All sound drivers that don't depend on PNP can be safelly
build with COMPILE_TEST, as ISA provides function stubs to
be used for such purposes.

As a side effect, with this change, the radio-miropcm20
can now be built outside i386 with COMPILE_TEST.

It should be noticed that ISAPNP currently depends on ISA.
So, on drivers that depend on it, we need to add an
explicit dependency on ISA, at least until another patch
removes it.

Acked-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>