Modernise _bfd_elf_mips_get_relocated_section_contents

In particular, bfd_get_full_section_contents rather than
bfd_get_section_contents so that compressed sections are handled
properly.

Necessary for mips if objdump is to not cache debug sections.

	* elfxx-mips.c (_bfd_elf_mips_get_relocated_section_contents): Apply
	all fixes to bfd_generic_get_relocated_section_contents since this
	function was split out.