s390: Simplify linker libgot-1 tests

s390: Simplify linker libgot-1 tests

This applies Alan's x86 commit df865c395a62 ("libgot-1 testcases")
simplifications to the respective s390 linker tests.  With Alan's words:

There is no need for multiple tests of readelf --got-contents,
nor should the matching be so strict that changes in section layout
force editing of the testsuite.

ld/testsuite/
	* ld-s390/binutils.exp (libgot-1*): Reduce number of tests.
	* ld-s390/libgot_64-1.rd: New test.
	* ld-s390/libgot_64-1a.rd: Remove.
	* ld-s390/libgot_64-1b.rd: Likewise.
	* ld-s390/libgot_64-1c.rd: Likewise.
	* ld-s390/libgot_64-1d.rd: Likewise.

Signed-off-by: Jens Remus <jremus@linux.ibm.com>