MIPS/BFD: Remove EI_ABIVERSION 5 allocation for PT_GNU_STACK support

Revert commit 17733f5be961 ("Increment the ABIVERSION to 5 for MIPS
objects with non-executable stacks.") and remove EI_ABIVERSION 5
allocation for PT_GNU_STACK support, which has not made it to glibc
and will be reassigned.

	bfd/
	* bfd/elfxx-mips.c (_bfd_mips_post_process_headers): Revert
	2016-02-23 change and remove EI_ABIVERSION 5 support.

(cherry picked from commit 4d4f40e041ce7c8c7c8e50f957e0440b64ab7e95)
2 files changed