gas/ia64: fix testsuite failures

gas/ia64: fix testsuite failures

Commit dd90581873 ("Place .shstrtab section after .symtab and .strtab,
thus restoring monotonically incre... ") adjusted section numbers, but
forgot to adjust sh_link references from relocation and group section
table entries.

Additionally some other (perhaps subsequent) change appears to have
added .rel.* and .rela.* sections to their respective groups, which
requires some further adjustments to group-2.d. I assume this additional
breakage wasn't noticed because the test was already failing at that
time.

This makes the gas testsuite complete successfully again for me in a
cross build on ix86-linux; there continue to be quite a few ld failures.