S/390: Support z14 as CPU name.

S/390: Support z14 as CPU name.

With IBM z14 officially announced I can add z14 as CPU name.

No regressions with that patch on s390x.

gas/ChangeLog:

2017-07-21  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* config/tc-s390.c (s390_parse_cpu): Add z14 as alternate CPU
	name.
	* doc/as.texinfo: Add z14 to CPU string list.
	* doc/c-s390.texi: Likewise.

opcodes/ChangeLog:

2017-07-21  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* s390-mkopc.c (main): Enable z14 as CPU string in the opcode
	table.