drm/xe: Remove unused functions

drm/xe: Remove unused functions

xe_bo_create_from_data() last use was removed in 2023 by
commit 0e1a47fcabc8 ("drm/xe: Add a helper for DRM device-lifetime BO
create")

xe_rtp_match_first_gslice_fused_off() last use was removed in 2023 by
commit 4e124151fcfc ("drm/xe/dg2: Drop pre-production workarounds")

Remove them, and xe_dss_mask_empty whose last use was by
xe_rtp_match_first_gslice_fused_off().

(Xe has a bunch ofother symbols that have been added but not used,
given how new it is, I've left those, as opposed to these that
had the code that used them removed).

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Link: https://lore.kernel.org/r/20250713152531.219326-1-linux@treblig.org
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>