The flags variable was being used uninitialized.
Initialize it to 0 as expected.
For some reason neither gcc nor clang reported a warning.
Fixes: ce2b276ebe51 ("s390/mm/fault: Handle guest-related program interrupts in KVM")
Reported-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>