Revert "drm/ttm: Add a flag to allow drivers to skip clear-on-free"

Remove TTM_TT_FLAG_CLEARED_ON_FREE now that XE stopped using this
flag.

This reverts commit decbfaf0.

Cc: Christian König <christian.koenig@amd.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240828083635.23601-2-nirmoy.das@intel.com


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