ARM: Don't define _SYS_AUXV_H in sysdep.h

ARM: Don't define _SYS_AUXV_H in sysdep.h

sysdep.h was defining _SYS_AUXV_H in order to avoid an include guard check
in hwcap.h. Unfortunately it didn't undefine it so it could leak out into
code and caused a build failure with -Wimplicit-function-declaration
building tst-auxv on ARM.

ChangeLog:

2014-09-23  Will Newton  <will.newton@linaro.org>

	* sysdeps/unix/sysv/linux/arm/bits/hwcap.h: Check for
	_LINUX_ARM_SYSDEP_H include guard too.
	* sysdeps/unix/sysv/linux/arm/sysdep.h (_SYS_AUXV_H): Remove
	define.