IBM Z: Do not run long double tests on old machines

IBM Z: Do not run long double tests on old machines

gcc/testsuite/ChangeLog:

2020-11-12  Ilya Leoshkevich  <iii@linux.ibm.com>

	* gcc.target/s390/s390.exp (check_effective_target_s390_z14_hw):
	New predicate.
	* gcc.target/s390/vector/long-double-caller-abi-run.c: Use the
	new predicate.
	* gcc.target/s390/vector/long-double-copysign.c: Likewise.
	* gcc.target/s390/vector/long-double-from-double.c: Likewise.
	* gcc.target/s390/vector/long-double-from-float.c: Likewise.
	* gcc.target/s390/vector/long-double-from-i16.c: Likewise.
	* gcc.target/s390/vector/long-double-from-i32.c: Likewise.
	* gcc.target/s390/vector/long-double-from-i64.c: Likewise.
	* gcc.target/s390/vector/long-double-from-i8.c: Likewise.
	* gcc.target/s390/vector/long-double-from-u16.c: Likewise.
	* gcc.target/s390/vector/long-double-from-u32.c: Likewise.
	* gcc.target/s390/vector/long-double-from-u64.c: Likewise.
	* gcc.target/s390/vector/long-double-from-u8.c: Likewise.
	* gcc.target/s390/vector/long-double-to-double.c: Likewise.
	* gcc.target/s390/vector/long-double-to-float.c: Likewise.
	* gcc.target/s390/vector/long-double-to-i16.c: Likewise.
	* gcc.target/s390/vector/long-double-to-i32.c: Likewise.
	* gcc.target/s390/vector/long-double-to-i64.c: Likewise.
	* gcc.target/s390/vector/long-double-to-i8.c: Likewise.
	* gcc.target/s390/vector/long-double-to-u16.c: Likewise.
	* gcc.target/s390/vector/long-double-to-u32.c: Likewise.
	* gcc.target/s390/vector/long-double-to-u64.c: Likewise.
	* gcc.target/s390/vector/long-double-to-u8.c: Likewise.
	* gcc.target/s390/vector/long-double-wfaxb.c: Likewise.
	* gcc.target/s390/vector/long-double-wfdxb.c: Likewise.
	* gcc.target/s390/vector/long-double-wfsxb-1.c: Likewise.