Revert "common.h: remove value from bool defines"

This reverts commit 914c9ee9
which is causing tons of build warnings like
start.S:39:0: warning: "_LINUX_CONFIG_H" redefined [enabled by
default]
/home/wd/git/u-boot/work/include/common.h:28:0: note: this is the
location of the previous definition
/work/wd/tmp-ppc/nand_spl/board/freescale/mpc8315erdb/start.S:39:0:
warning: "_LINUX_CONFIG_H" redefined [enabled by default]
/home/wd/git/u-boot/work/include/common.h:28:0: note: this is the
location of the previous definition
etc.

Signed-off-by: Wolfgang Denk <wd@denx.de>