drm/xe: Allow compressible surfaces to be 1-way coherent

drm/xe: Allow compressible surfaces to be 1-way coherent

Previously, compressible surfaces were required to be non-coherent
(allocated as WC) because compression and coherency were mutually
exclusive. Starting with Xe3, hardware supports combining compression
with 1-way coherency, allowing compressible surfaces to be allocated as
WB memory. This provides applications with more efficient memory
allocation by avoiding WC allocation overhead that can cause system
stuttering and memory management challenges.

The implementation adds support for compressed+coherent PAT entry for
the xe3_lpg devices and updates the driver logic to handle the new
compression capabilities.

v2: (Matthew Auld)
 - Improved error handling with XE_IOCTL_DBG()
 - Enhanced documentation and comments
 - Fixed xe_bo_needs_ccs_pages() outdated compression assumptions

v3:
 - Improve WB compression support detection by checking PAT table
   instead of version check

v4:
 - Add XE_CACHE_WB_COMPRESSION, which simplifies the logic.

v5:
 - Use U16_MAX for the invalid PAT index. (Matthew Auld)

Bspec: 71582, 59361, 59399
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Xin Wang <x.wang@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patch.msgid.link/20260109093007.546784-1-x.wang@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>