arm64: locks: introduce ticket-based spinlock implementation

This patch introduces a ticket lock implementation for arm64, along the
same lines as the implementation for arch/arm/.

Change-Id: Ic4603f7814a9787d452741d45d921a92602212b7
Reviewed-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/next/linux-next.git


Git-commit: 52ea2a560a9dba57fe5fd6b4726b1089751accf2
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>