drm/xe/wopcm: fix WOPCM size for LNL+

drm/xe/wopcm: fix WOPCM size for LNL+

Starting on LNL the WOPCM size is 8MB instead of 4, so we need to avoid
using the [0, 8MB) range of the GGTT as that can be unaccessible from
the microcontrollers.

Note that the proper long-term fix here is to read the WOPCM size from
the HW, but that is a more serious rework that would be difficult to
backport, so we can do that as a follow-up.

Fixes: 9c57bc08652a ("drm/xe/lnl: Drop force_probe requirement")
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Shuicheng Lin <shuicheng.lin@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Shuicheng Lin <shuicheng.lin@intel.com>
Link: https://patch.msgid.link/20260713221758.3285744-2-daniele.ceraolospurio@intel.com
(cherry picked from commit 3033b0b24ed0e2f5e56bdd4d9c183417c365a45b)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>