cpu/cpu.h: Drop excessive includes

Change-Id: Ifeef04b68760522ce7f230a51f5df354e6da6607
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/17734
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
32 files changed