PR28751 mbind2a / mbind2b regressions on powerpc*-linux

include/
	* bfdlink.h (struct bfd_link_info): Add commonpagesize_is_set.
ld/
	PR 28751
	* emultempl/elf.em (handle_option): Set commonpagesize_is_set.
	* ldelf.c (ldelf_after_parse): Don't error when only one of
	-z max-page-size or -z common-page-size is given, correct the
	other value to make it sane.
	* testsuite/ld-elf/elf.exp (mbind2a, mbind2b): Do not pass
	-z max-page-size.