drm/xe/vm: move xe_svm_init() earlier

drm/xe/vm: move xe_svm_init() earlier

In xe_vm_close_and_put() we need to be able to call xe_svm_fini(),
however during vm creation we can call this on the error path, before
having actually initialised the svm state, leading to various splats
followed by a fatal NPD.

Fixes: 6fd979c2f331 ("drm/xe: Add SVM init / close / fini to faulting VMs")
Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4967
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250514152424.149591-4-matthew.auld@intel.com