arm64: kconfig: select HAVE_CMPXCHG_LOCAL

We implement an optimised cmpxchg_local macro, so let the kernel know.

Reviewed-by: Steve Capper <steve.capper@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>