s390/perf: obtain sie_block from the right address

s390/perf: obtain sie_block from the right address

Since commit 1179f170b6f0 ("s390: fix fpu restore in entry.S"), the
sie_block pointer is located at empty1[1], but in sie_block() it was
taken from empty1[0].

This leads to a random pointer being dereferenced, possibly causing
system crash.

This problem can be observed when running a simple guest with an endless
loop and recording the cpu-clock event:

  sudo perf kvm --guestvmlinux=<guestkernel> --guest top -e cpu-clock

With this fix, the correct guest address is shown.

Fixes: 1179f170b6f0 ("s390: fix fpu restore in entry.S")
Cc: [email protected]
Acked-by: Christian Borntraeger <[email protected]>
Acked-by: Claudio Imbrenda <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Signed-off-by: Nico Boehr <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>