vfio: ccw: process ssch with interrupts disabled

vfio: ccw: process ssch with interrupts disabled

When we call ssch, an interrupt might already be pending once we
return from the START SUBCHANNEL instruction. Therefore we need to
make sure interrupts are disabled while holding the subchannel lock
until after we're done with our processing.

Cc: [email protected] #v4.12+
Reviewed-by: Dong Jia Shi <[email protected]>
Acked-by: Halil Pasic <[email protected]>
Acked-by: Pierre Morel <[email protected]>
Signed-off-by: Cornelia Huck <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>