s390x: Fix sclp console input

When injecting an sclp console interrupt into the guest, we increase
the PC by 4 for some reason. I have no idea why I put that code there,
but it's clearly wrong. Remove the increment.

This patch fixes sclp serial input for the ccw machine.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
s390x: Implement SAM{24,31,64}

The SAM instructions simply change 2 bits in PSW.MASK to advertise
the current memory mode. While we can't fully guarantee that 31 bit
mode (or even remotely 24 bit mode) actually work correctly, we don't
check whether lpswe modifies these bits, so we shouldn't keep the
guest from executing SAM instructions either.

This patch implements all SAM instrutions with their actual PSW changing
semantics, making more recent Linux kernels boot properly which do issue
a SAM31 call during early boot.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Reviewed-by: Richard Henderson <rth@twiddle.net>