Mark xe driver as BROKEN if kernel page size is not 4kB

Mark xe driver as BROKEN if kernel page size is not 4kB

This driver, for the time being, assumes that the kernel page size is 4kB,
so it fails on loong64 and aarch64 with 16kB pages, and ppc64el with 64kB
pages.

Signed-off-by: Simon Richter <Simon.Richter@hogyros.de>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Cc: stable@vger.kernel.org # v6.8+
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://lore.kernel.org/r/20250802024152.3021-1-Simon.Richter@hogyros.de