s390: fix htm-builtins test cases

Transactional and non-transactional stores to the same cache line cause
transactions to abort on newer generations.  Add sufficient padding to make
sure another cache line is used.

Tested on s390.

gcc/testsuite/ChangeLog:

	* gcc.target/s390/htm-builtins-1.c: Fix.
	* gcc.target/s390/htm-builtins-2.c: Fix.

Signed-off-by: Juergen Christ <jchrist@linux.ibm.com>