mcslock: add MCS queued lock implementation

mcslock: add MCS queued lock implementation

If there are multiple threads contending, they all attempt to take the
spinlock lock at the same time once it is released. This results in a
huge amount of processor bus traffic, which is a huge performance
killer. Thus, if we somehow order the lock-takers so that they know who
is next in line for the resource we can vastly reduce the amount of bus
traffic.

This patch added MCS lock library. It provides scalability by spinning
on a CPU/thread local variable which avoids expensive cache bouncings.
It provides fairness by maintaining a list of acquirers and passing the
lock to each CPU/thread in the order they acquired the lock.

Signed-off-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>