common/lcd: Add command for setting cursor within lcd-console

Sometimes we do not want redirect u-boot's console to screen but anyway we want
write out some status information out of a u-boot script to the display.

To define the specific position of the string to be written, we have to set
the cursor with "setcurs" before writing.

Signed-off-by: Hannes Petermaier <oe5hpm@oevsv.at>