[ARM] Introduce SMP operations common for all boards

The architecture SMP callbacks implemented by various boards
have lot of similarities. Further, we did not use any host CPU
related info passed to Xvisor via DTB.

This patch introduces common SMP operations framework for
all ARM boards. The patch also adds common implemenation of
SMP operations for SCU and Spin Table SMP booting methods.

Signed-off-by: Anup Patel <anup@brainfault.org>