MIPS/LD/testsuite: Fix MIPS16 interlinking test n64 regressions

MIPS/LD/testsuite: Fix MIPS16 interlinking test n64 regressions

The MIPS16 interlinking test for local functions expects to be assembled
with 32-bit addressing, otherwise causing assembly warnings:

.../ld/testsuite/ld-mips-elf/mips16-local-stubs-1.s: Assembler messages:
.../ld/testsuite/ld-mips-elf/mips16-local-stubs-1.s:16: Warning: la used to load 64-bit address; recommend using dla instead

Use the per-ABI framework then to run the test explicitly for o32 and
n32 ABIs only, replacing the `-mips4' option from the `as' tag with
`.module mips4' pseudo-op within the source itself so as to avoid
assembly errors:

Assembler messages:
Error: -mips4 conflicts with the other architecture options, which imply -mips3

with n32 testing for some targets, and ultimately removing these
regressions:

mips64-openbsd  -FAIL: MIPS16 interlinking for local functions 1
mips64el-openbsd  -FAIL: MIPS16 interlinking for local functions 1

Co-Authored-By: Maciej W. Rozycki <macro@orcam.me.uk>
	ld/
	* testsuite/ld-mips-elf/mips16-local-stubs-1.d: Remove `-mips4'
	from the `as' tag.
	* testsuite/ld-mips-elf/mips16-local-stubs-1.s: Add `.module
	mips4'.
	* testsuite/ld-mips-elf/mips-elf.exp: Run `mips16-local-stubs-1'
	for o32 and n32 ABIs only.