MIPS/BFD: Remove duplicate NewABI JALR relocation handling

MIPS/BFD: Remove duplicate NewABI JALR relocation handling

Remove separate original NewABI JALR relocation handling, introduced
with commit d06471104a83 ("relax jalr $t9 [R_MIPS_JALR symbol] to bal
symbol"), <https://sourceware.org/ml/binutils/2003-03/msg00394.html>,
and only used by LD with the `--relax' option specified, and rely solely
on `mips_elf_perform_relocation' code, which has been introduced with
commit 1367d393bb74 ("On the RM9000 convert jal to bal if in range"),
<https://www.sourceware.org/ml/binutils/2004-12/msg00088.html> and since
made more complete, across all the three ABIs.

Also remove the `--relax' option, now irrelevant, from the tests added
with the former commit.

	bfd/
	* elfxx-mips.h (_bfd_mips_relax_section): Remove prototype.
	* elfxx-mips.c (_bfd_mips_relax_section): Remove function.
	* elf64-mips.c (bfd_elf64_bfd_relax_section): Remove macro.
	* elfn32-mips.c (bfd_elf32_bfd_relax_section): Likewise.

	ld/
	* testsuite/ld-mips-elf/relax-jalr-n32.d: Remove `--relax'
	option.
	* testsuite/ld-mips-elf/relax-jalr-n32-shared.d: Likewise.
	* testsuite/ld-mips-elf/relax-jalr-n64.d: Likewise.
	* testsuite/ld-mips-elf/relax-jalr-n64-shared.d: Likewise.