drm/xe/debugfs: Make residencies definitions const

drm/xe/debugfs: Make residencies definitions const

No need to keep them non-const. Also fix declaration of .name
member, as it points to the const string. This translates to:

  add/remove: 1/0 grow/shrink: 0/2 up/down: 80/-248 (-168)
  Function                                     old     new   delta
  residencies                                    -      80     +80
  dgfx_pcie_link_residencies_show              365     263    -102
  dgfx_pkg_residencies_show                    454     308    -146
  Total: Before=2821548, After=2821380, chg -0.01%

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Soham Purkait <soham.purkait@intel.com>
Cc: Jonathan Cavitt <jonathan.cavitt@intel.com>
Cc: Karthik Poosa <karthik.poosa@intel.com>
Cc: Riana Tauro <riana.tauro@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20250905180225.8434-1-michal.wajdeczko@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>