s390: Explicitly list linker dump tests

s390: Explicitly list linker dump tests

Generating the linker dump test list using file globbing makes it
difficult to exclude specific tests under certain circumstances.  List
them explicitly instead.  This enables to add tests in the future that
can be excluded.  While at it reorganize how s390 linker tests get
run for s390x.

ld/testsuite/
	* ld-s390/s390.exp: Reorganize and explicitly list linker dump
	tests.

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