build: separate CPPFLAGS from CFLAGS

There are a couple of places where CPPFLAGS are
pasted into CFLAGS, eliminate them.

Change-Id: Ic7f568cf87a7d9c5c52e2942032a867161036bd7
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/5765
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
11 files changed