firmware: scm: Add new SCM call API for switching memory ownership

Two different processors on a SOC need to switch memory ownership
during load/unload. To enable this, second level memory map table
need to be updated, which is done by secure layer.
This patch adds the interface for making secure monitor call for
memory ownership switching request.

Acked-by: Andy Gross <andy.gross@linaro.org>
Signed-off-by: Avaneesh Kumar Dwivedi <akdwived@codeaurora.org>
[bjorn: Minor style and kerneldoc updates]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>