drm/xe: Add missing _H to include guard suffixes

drm/xe: Add missing _H to include guard suffixes

Ten headers use _XE_<NAME>_ or __XE_<NAME>__ as their include guard but
omit the _H that the rest of the xe codebase uses. Normalize them to
_XE_<NAME>_H_ to follow the dominant convention (_XE_<BASENAME>_H_) used
by ~232 of ~260 xe headers.

Files fixed:
  - xe_migrate.h:       _XE_MIGRATE_       -> _XE_MIGRATE_H_
  - xe_pt_walk.h:       __XE_PT_WALK__     -> _XE_PT_WALK_H_
  - xe_reg_sr.h:        _XE_REG_SR_        -> _XE_REG_SR_H_
  - xe_reg_sr_types.h:  _XE_REG_SR_TYPES_  -> _XE_REG_SR_TYPES_H_
  - xe_reg_whitelist.h: _XE_REG_WHITELIST_ -> _XE_REG_WHITELIST_H_
  - xe_rtp.h:           _XE_RTP_           -> _XE_RTP_H_
  - xe_rtp_helpers.h:   _XE_RTP_HELPERS_   -> _XE_RTP_HELPERS_H_
  - xe_rtp_types.h:     _XE_RTP_TYPES_     -> _XE_RTP_TYPES_H_
  - xe_tuning.h:        _XE_TUNING_        -> _XE_TUNING_H_
  - xe_wa.h:            _XE_WA_            -> _XE_WA_H_

No functional change.

Suggested-by: Nitin Gote <nitin.r.gote@intel.com>
Assisted-by: GitHub Copilot:claude-opus-4.6
Reviewed-by: Nitin Gote <nitin.r.gote@intel.com>
Link: https://patch.msgid.link/20260317215732.2208976-9-shuicheng.lin@intel.com
Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>