drm/i915/dp: Return int from dsc_max/min_src_input_bpc helpers

Use ints for dsc_max/min_bpc instead of u8 in
dsc_max/min_src_input_bpc helpers and their callers.
This will also help replace min_t/max_t macros with min/max ones.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241217093244.3938132-7-ankit.k.nautiyal@intel.com