MIPS: Fix a R10000_LLSC_WAR logic in atomic.h

Commit 4936084c ("MIPS: Cleanup R10000_LLSC_WAR logic in atomic.h")
introduce a mistake in atomic64_fetch_##op##_relaxed(), because it
forget to delete R10000_LLSC_WAR in the if-condition. So fix it.

Fixes: 4936084c ("MIPS: Cleanup R10000_LLSC_WAR logic in atomic.h")
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Joshua Kinard <kumba@gentoo.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Steven J . Hill <Steven.Hill@cavium.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org # 4.19+