drm/xe/mocs: Update MOCS assertions and remove redundant checks

Rely more heavily on assertions to describe the MOCS programming
invariants.  CI checks these assertions and will ensure no violations
sneak in due to programmer error, so we can remove some of the redundant
WARN and silent return checks from non-debug builds.

Also tweak/augment some of the existing assertions: there's no reason
we'd ever want a platform not to have a MOCS 'ops' structure hooked up
so ensure info->ops is non-NULL.  Likewise, we should never have a case
where the bspec-defined MOCS setting table is larger than the number of
MOCS registers exposed by the hardware, so add an extra assert on those
sizes as well.

Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240627203741.2042752-3-matthew.d.roper@intel.com