ACPI / resources: free memory on error in add_region_before()

There is a small memory leak on error.

Fixes: 0f1b414d (ACPI / PNP: Avoid conflicting resource reservations)
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>