common: image.c: Fix CACHE: Misaligned operation output

When booting a itb file with a Ramdisk on a imx6 based
board, U-Boot drops the warning:

Loading Kernel Image ... OK
Loading Ramdisk to 4ecf1000, end 4ef8b11f ... \
CACHE: Misaligned operation at range [4ecf1000,  4ef8b11f]

Fix it!

Signed-off-by: Heiko Schocher <hs@denx.de>
Tested-by: Ayoub Zaki <hs@denx.de>