MIPS/BFD: Remove EI_ABIVERSION 5 allocation for PT_GNU_STACK support

Revert commit 17733f5be9 ("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.

bfd/ChangeLog

@@ -1,3 +1,8 @@
+2016-12-23  Maciej W. Rozycki  <macro@imgtec.com>
+
+	* bfd/elfxx-mips.c (_bfd_mips_post_process_headers): Revert
+	2016-02-23 change and remove EI_ABIVERSION 5 support.
+
 2016-12-23  Alan Modra  <amodra@gmail.com>
 
 	* linker.c (generic_link_check_archive_element): Call target

bfd/elfxx-mips.c

@@ -16358,9 +16358,6 @@ _bfd_mips_post_process_headers (bfd *abfd, struct bfd_link_info *link_info)
   if (mips_elf_tdata (abfd)->abiflags.fp_abi == Val_GNU_MIPS_ABI_FP_64
       || mips_elf_tdata (abfd)->abiflags.fp_abi == Val_GNU_MIPS_ABI_FP_64A)
     i_ehdrp->e_ident[EI_ABIVERSION] = 3;
-
-  if (elf_stack_flags (abfd) && !(elf_stack_flags (abfd) & PF_X))
-    i_ehdrp->e_ident[EI_ABIVERSION] = 5;
 }
 
 int