drm/xe/uapi: Fix wrong names and references in xe_drm.h

drm/xe/uapi: Fix wrong names and references in xe_drm.h

Fix incorrect field names, struct names, ioctl names, and
descriptions in doc comments:
- probed_size -> @cpu_visible_size (correct field name)
- @flags description was copy of @placement ->
  fix to reference DRM_XE_GEM_CREATE_FLAG_*
- %XE_PXP_HWDRM_DEFAULT_SESSION ->
  %DRM_XE_PXP_HWDRM_DEFAULT_SESSION (missing DRM_ prefix)
- Remove undefined %DRM_XE_UFENCE_WAIT_FLAG_SOFT_OP
- &DRM_XE_OBSERVATION -> &DRM_IOCTL_XE_OBSERVATION
- id's/struct's -> IDs/structs (fix incorrect possessive forms)
- drm_xe_query_oa_units -> drm_xe_oa_unit
- DRM_IOCTL_XE_VM_QUERY_MEM_RANGES_ATTRS ->
  DRM_IOCTL_XE_VM_QUERY_MEM_RANGE_ATTRS
- DRM_IOCTL_XE_VM_QUERY_MEM_ATTRIBUTES ->
  DRM_IOCTL_XE_VM_QUERY_MEM_RANGE_ATTRS
- @sizeof_mem_ranges_attr -> @sizeof_mem_range_attr
- @vector_of_vma_mem_attr -> @vector_of_mem_attr

v3: id -> ID. (Xin)
    split cross-reference fix to seperate patch.

Assisted-by: GitHub Copilot:claude-opus-4.6
Cc: Xin Wang <x.wang@intel.com>
Reviewed-by: Xin Wang <x.wang@intel.com>
Link: https://patch.msgid.link/20260407030046.3394004-4-shuicheng.lin@intel.com
Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>