[media] img-ir: Depend on METAG or MIPS or COMPILE_TEST

The ImgTec Infrared decoder block which img-ir drives is only used in
IMGWorks SoCs so far, such as the TZ1090 (Meta based) and the upcoming
Pistachio (MIPS based). Therefore make the driver depend on METAG (for
TZ1090) or MIPS (for Pistachio) or COMPILE_TEST (so that it is included
in x86 allmodconfig builds), to avoid cluttering the Kconfig menu with
drivers for hardware that isn't yet available on other platforms.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>