dax/bus: Use dax_region_put() in alloc_dax_region() error path

alloc_dax_region() calls kref_init() on the dax_region early in the
function, but the error path for sysfs_create_groups() failure uses
kfree() directly to free the dax_region. This bypasses the kref lifecycle.

Use dax_region_put() instead to handle kref lifecycle correctly.

Suggested-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260322195343.206900-2-Smita.KoralahalliChannabasappa@amd.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>