arm64: initialize secmon environment

arm64: initialize secmon environment

The exception vectors were not reinitialized in secmon yet.
Add that as well as the split BSP vs non-BSP path. In doing
so bring in the cpu.c semantics for determining bsp at runtime.

BUG=chrome-os-partner:30785
BRANCH=None
TEST=Built and booted to kernel. Also noted only one CPU
     printing messages.

Change-Id: I26a7f9446f4422d2203b1d520e69f8dee9450b59
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 67f79c61c902ee614f029047255b4be35112cd32
Original-Change-Id: Ide66f13c24f5798d5983c481ce616ae2800d558c
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/218845
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/9091
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>