media: verisilicon: Do not set ctx->bit_depth in hantro_try_ctrl()

In hantro_try_ctrl() we should only check the values inside
control parameters and not set ctx->bit_depth. That must
be done in controls set function.
Create a set control function for hevc where ctx->bit_depth is
set at the right time.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>