drm/xe: Accept a const xe device

Depending on the context, it's preferred to have a const pointer to make
sure nothing is modified underneath. The assert macros only ever read
data from xe/tile/gt for printing, so they can be made const by default.

Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20230922174320.2372617-1-lucas.demarchi@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>