Move away from the __ARCH_WANT_SYSCALL_NO_AT system calls.

Modern architectures only get the *at(2) system calls. For example,
aarch64 doesn't have open(2), and expects userspace to use openat(2)
instead.

Change-Id: I87b4ed79790cb8a80844f5544ac1a13fda26c7b5
100 files changed