[S390] fix kprobes single stepping

Fix kprobes after git commit 1e54622e0403891b10f2105663e0f9dd595a1f17
broke it. The kprobe_handler is now called with interrupts in the state
at the time of the breakpoint. The single step of the replaced instruction
is done with interrupts off which makes it necessary to enable and disable
the interupts in the kprobes code.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --cc arch/s390/kernel/entry.S
Simple merge

diff --cc arch/s390/kernel/entry64.S
Simple merge

diff --cc arch/s390/kernel/kprobes.c
Simple merge