psci system_reset and system_off calls now retrieve shutdown scope on
the fly. The default scope is system, but it can be changed by calling
pm_system_shutdown(2, scope)

Until full support for different restart scopes becomes available with
PSCI 1.1 this change allows users to set the reboot scope to match
their application needs.

Possible scope values:
0 - APU subsystem: does not affect RPU, PMU or PL
1 - PS only: shutdown/restart entire PS without affecting PL
2 - System: shutdown/restart applies to entire system

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Davorin Mista <davorin.mista@aggios.com>