board: sandburst: delete FORCEBUILD

We had switched to Kbuild, so we do not need to
delete sandburst board files at every build.

U-Boot conventional build system did not check the
update of command line option, -DBUILDUSER.

Kbuild can handle it nicely and re-builds object files
when command line options are changed.
(The file ".*.cmd" stores the information how the file
was generated at the previous build.)

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

board/sandburst/karef/Makefile

@@ -10,11 +10,7 @@
 #
 
 # TBS: add for debugging purposes
-BUILDUSER := $(shell whoami)
-FORCEBUILD := $(shell rm -f karef.o)
-
-ccflags-y += -DBUILDUSER='"$(BUILDUSER)"'
-# TBS: end debugging
+ccflags-y += -DBUILDUSER='"$(shell whoami)"'
 
 obj-y	= karef.o ../common/flash.o ../common/sb_common.o
 extra-y	+= init.o

board/sandburst/metrobox/Makefile

@@ -9,11 +9,7 @@
 #
 
 # TBS: add for debugging purposes
-BUILDUSER := $(shell whoami)
-FORCEBUILD := $(shell rm -f metrobox.o)
-
-ccflags-y += -DBUILDUSER='"$(BUILDUSER)"'
-# TBS: end debugging
+ccflags-y += -DBUILDUSER='"$(shell whoami)"'
 
 obj-y	= metrobox.o ../common/flash.o ../common/sb_common.o
 extra-y	+= init.o