s390/con3270: fix formatting issues

fix function prototypes split over two lines like:

static void
foobar(void)

and fix superfluous spaces in declarations like

foo * bar

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