drm/xe: Keep all defaults in single header

drm/xe: Keep all defaults in single header

We already have most of Xe defaults defined in xe_module.c,
where we use them for the modparam initializations, but some
were defined elsewhere, which breaks the consistency.

Introduce xe_defaults.h file, that will act as a placeholder
for all our default values, and can be used from other places.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patch.msgid.link/20260121214218.2817-2-michal.wajdeczko@intel.com