Both libc/include/sys/auxv.h and libc/private/bionic_auxv.h
use _SYS_AUXV_H_ to see if a header file has already been included.
This prevents both of these files from being included at the same
time.
Fix this name conflict.
Change-Id: Ifaec88aa9779d784b95f8e75145117acf3d5cfc5