media: rp1: fe: Fix pisp_fe_pad_set_fmt()

pisp_fe_pad_set_fmt() allows setting the pad formats quite freely. This
is not correct, and the function should only allow formats as supported
by the hardware. Fix this by:

Allow no format changes for FE_CONFIG_PAD and FE_STATS_PAD. They should
always be the hardcoded initial ones.

Allow setting FE_STREAM_PAD freely (but the mbus code must be
supported), and propagate the format to the FE_OUTPUT0_PAD and
FE_OUTPUT1_PAD pads.

Allow changing the mbus code for FE_OUTPUT0_PAD and FE_OUTPUT1_PAD pads
only if the mbus code is the compressed version of the sink side code.

TODO: FE supports scaling and cropping. This should be represented here
too?

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>