s390: Add scheduler description for z16.

s390: Add scheduler description for z16.

This patch adds the scheduler description for the z16 machine.

gcc/ChangeLog:

	* config/s390/s390.cc (s390_get_sched_attrmask): Add z16.
	(s390_get_unit_mask): Likewise.
	(s390_is_fpd): Likewise.
	(s390_is_fxd): Likewise.
	* config/s390/s390.h (s390_tune_attr): Set max tune level to z16.
	* config/s390/s390.md (z900,z990,z9_109,z9_ec,z10,z196,zEC12,z13,z14,z15):
	Add z16.
	(z900,z990,z9_109,z9_ec,z10,z196,zEC12,z13,z14,z15,z16):
	Likewise.
	* config/s390/3931.md: New file.