[PR ld/22269] arm: Avoid dynamic relocs for undefweak symbols in static PIE

With static PIE linking undefined weak symbols are resolved to 0, so no
dynamic relocation is needed for them. The UNDEFWEAK_NO_DYNAMIC_RELOC
macro was introduced so this case can be handled easily, but it was not
applied consistently in the first attempt to fix ld/22269 for arm:

  commit 95b03e4a
  arm: Check UNDEFWEAK_NO_DYNAMIC_RELOC

This patch fixes spurious relative relocs in static PIE binaries against
GOT entries created for undefined weak symbols on arm*-*, this fixes

FAIL: pr22269-1 (static pie undefined weak)

bfd/ChangeLog:

	Backported from master
	2020-01-10  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	PR ld/22269
	* elf32-arm.c (elf32_arm_final_link_relocate): Use
	UNDEFWEAK_NO_DYNAMIC_RELOC.
	(allocate_dynrelocs_for_symbol): Likewise.