drm/xe: Retain vma flags when recreating and splitting vmas for madvise

drm/xe: Retain vma flags when recreating and splitting vmas for madvise

When splitting and restoring vmas for madvise, we only copied the
XE_VMA_SYSTEM_ALLOCATOR flag. That meant we lost flags for read_only,
dumpable and sparse (in case anyone would call madvise for the latter).

Instead, define a mask of relevant flags and ensure all are replicated,
To simplify this and make the code a bit less fragile, remove the
conversion to VMA_CREATE flags and instead just pass around the
gpuva flags after initial conversion from user-space.

Fixes: a2eb8aec3ebe ("drm/xe: Reset VMA attributes to default in SVM garbage collector")
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20251015170726.178685-1-thomas.hellstrom@linux.intel.com