bfd/elfnn-aarch64.c: Remove elfNN_aarch64_section_flags

This function seems to be a left over from some previous
functionality that no longer exists - the comment above seems to
make no sense with the current code. Remove the function as it
breaks handling of SystemTap static probe note sections.

bfd/ChangeLog:

2014-04-22  Will Newton  <will.newton@linaro.org>

	* elfnn-aarch64.c (elfNN_aarch64_section_flags): Remove
	function.  (elf_backend_section_flags): Remove define.