drm/xe: Use platform name in xe_assert()

We can now use more user-friendly platform name instead of
previosly used magic platform enumerator value:

  [ ] xe 0000:00:02.0: [drm] Assertion `false` failed!
      platform: ALDERLAKE_S ...
  [ ] xe 0000:03:00.0: [drm] Assertion `false` failed!
      platform: DG2 ...

vs

  [ ] xe 0000:00:02.0: [drm] Assertion `false` failed!
      platform: 3 ...
  [ ] xe 0000:03:00.0: [drm] Assertion `false` failed!
      platform: 7 ...

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240521142257.756-4-michal.wajdeczko@intel.com