media: meson: vdec: add g12a platform

Add support for the G12A platform by:
- adding the G12A codec support, here MPEG1 & MPEG2
- getting the new hevcf clock for the upcoming HEVC/VP9 decoding support

Signed-off-by: Maxime Jourdan <mjourdan@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>