arm64: barriers: use barrier() instead of smp_mb() when !SMP

The recently introduced acquire/release accessors refer to smp_mb()
in the !CONFIG_SMP case. This is confusing when reading the code, so use
barrier() directly when we know we're UP.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Git-commit: be6209a6107e0f63544e3e7d00fd5c95434ec80a
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>