This patch modifies the prototype of the bl1_plat_prepare_exit()
platform API to pass the address of the entry point info structure
received from BL2. The structure contains information that can be
useful, depending on the kind of clean up or bookkeeping operations
to perform.

The weak implementation of this function ignores this argument to
preserve platform backwards compatibility.

NOTE: THIS PATCH MAY BREAK PLATFORM PORTS THAT ARE RELYING ON THE
FORMER PROTOTYPE OF THE BL1_PLAT_PREPARE_EXIT() API.

Change-Id: I3fc18f637de06c85719c4ee84c85d6a4572a0fdb