video: Support multiple lines version string display

The calculation of left space for version string is not correct, should
use VIDEO_COLS not VIDEO_LINE_LEN / 2, otherwise we will get larger space
than actual have and cause string to overlay logo picture.

Also current version string display only supports two lines words at max.
This also causes overlay when the LCD pixel column size is not enough.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Tested-by: Anatolij Gustschin <agust@denx.de>