media: hantro: allow arbitrary number of clocks

Dynamically allocate clocks and move clock names out of struct
hantro_variant. This lifts the four clock limit and allows to use
ARRAY_SIZE() to fill .num_clocks to reduce the risk of mismatches.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>