Isolate Kconfig host compiler options

This reverts commit 645f2dd5d9.

Instead of adding a special case to nvramtool to avoid it
picking up Kconfig's regex.h, have the host compiler only
consider util/kconfig for includes (ie. -Iutil/kconfig)
for kconfig related object files.

Change-Id: Ie4f97ce38cb3e911f6e6c1e5b6f86f6998d93f69
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/1509
Tested-by: build bot (Jenkins)
Reviewed-by: Zheng Bao <zheng.bao@amd.com>
Reviewed-by: Anton Kochkov <anton.kochkov@gmail.com>

util/nvramtool/Makefile.inc

@@ -27,10 +27,6 @@ endif
 ifeq ($(OS_ARCH), NetBSD)
 NVRAMTOOLLDLFLAGS = -l$(shell uname -p)
 endif
-ifeq ($(OS_ARCH), FreeBSD)
-NVRAMTOOLFLAGS += -O2 -g -Wall -W
-HOSTCFLAGS =
-endif
 ifeq ($(shell uname -o), Cygwin)
 NVRAMTOOLFLAGS += -O2 -g -Wall -W -D__GLIBC__
 NVRAMTOOLLDFLAGS = -lioperm