This patch adds support to run a Trusted OS during boot time. The
previous stage bootloader passes the entry point information in
the 'bl32_ep_info' structure, which is passed over to the SPD.

The build system expects the dispatcher to be passed as an input
parameter using the 'SPD=<dispatcher>' option. The Tegra docs have
also been updated with this information.

Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>