drm/xe: Fix kernel-doc comment syntax issues in header files

drm/xe: Fix kernel-doc comment syntax issues in header files

Fix doc comment formatting that does not conform to kernel-doc syntax
rules:

- xe_guc_relay_types.h: Add missing space after '/**' in member doc
  comment (/**@lock -> /** @lock)
- xe_oa_types.h: Fix struct documentation to use proper kernel-doc
  format (/** @xe_oa_buffer: -> /** struct xe_oa_buffer -)
- xe_pagefault_types.h: Use dash instead of colon as separator in
  struct doc (struct xe_pagefault_queue: -> struct xe_pagefault_queue -)
- xe_pt_walk.h: Use dash instead of colon as separator in function
  docs (xe_pt_num_entries: -> xe_pt_num_entries -,
  xe_pt_offset: -> xe_pt_offset -)

Assisted-by: GitHub Copilot:claude-sonnet-4.6
Reviewed-by: Brian Nguyen <brian3.nguyen@intel.com>
Link: https://patch.msgid.link/20260414225457.3687449-4-shuicheng.lin@intel.com
Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>