locking/atomics: atomic-instrumented: simplify ifdeffery

Now that all architectures implement ARCH_ATOMIC, the fallbacks are
generated before the instrumented wrappers are generated. Due to this,
in atomic-instrumented.h we can assume that the whole set of atomic
functions has been generated. Likewise, atomic-instrumented.h doesn't
need to provide a preprocessor definition for every atomic it wraps.

This patch removes the redundant ifdeffery.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210525140232.53872-34-mark.rutland@arm.com