board/g2000/strataflash.c: fix GCC 4.6 build warnings

Fix:
strataflash.c: In function 'flash_write_cfiword':
strataflash.c:669:11: warning: variable 'ctladdr' set but not used
[-Wunused-but-set-variable]

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