aarch64: Set ilp32 minimum linux version to 4.12

Mainline linux does not support ilp32 yet, but there is support
for this abi since linux v4.12 in the arm64 linux repo under
ilp32 staging branches.

2017-09-01  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* sysdeps/unix/sysv/linux/aarch64/configure.ac (arch_minimum_kernel):
	Set to 4.12.0 on ILP32.
	* sysdeps/unix/sysv/linux/aarch64/configure: Regenerate.