drm/i915/dmc: check incoming dmc id validity

Add validity checks for the dmc ids computed from pipe parameters in
intel_dmc_enable_pipe() and intel_dmc_disable_pipe(). It's slightly
difficult for humans and static analyzers alike to ensure the resulting
dmc ids are within bounds. Just check them and reject invalid ones.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/6a349c3a2b2def5fc31a48c9844ebd72ee55a22b.1675339447.git.jani.nikula@intel.com