s390/con3270: set SBA and RA addresses when converting lines

Now that lines are converted during output, the RA and SBA no longer
need to get updated as an additional step. Instead set them when
converting the line.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>