AArch64: Use ELF macros rather than Elf64 throughout

Using the macros for ELF types is required for adding ILP32 support.
In the standard AArch64 configuration this makes no difference to
the types used.

ChangeLog:

2014-11-21  Will Newton  <will.newton@linaro.org>
	    Andrew Pinski  <andrew.pinski@caviumnetworks.com>

	* sysdeps/aarch64/bits/link.h (la_aarch64_gnu_pltenter): Use
	ElfW macro instead of hardcoded Elf64 types.
	(la_aarch64_gnu_pltenter): Likewise.
	* sysdeps/aarch64/dl-machine.h
	(elf_machine_runtime_setup): Use ElfW(Addr).