drivers: scm: Add SCM call support to set warmboot addr

Add the SCM call support for core hotplug and set warmboot address
for multi core.

Change-Id: I747858d1ffc1008b6d9033526110c98a3bb2401b
Signed-off-by: Raghavendra Kakarla <rkakarla@codeaurora.org>
Signed-off-by: Tushar Nimkar <tnimkar@codeaurora.org>