drivers/base: cpu: Add node for cpu isolation

Add a new per-cpu node to control isolation of CPU.

Usage:
echo 1 > isolate - Isolate the core
echo 0 > isolate - Unisolate the core

Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
[markivx: Adjust for lack of HMP]
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>

Change-Id: I11385d8072f8fa6e69b58588bf6996a16ebf3d35
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>