s390/uprobes: fix compile for !KPROBES

Fix the following compile error(s) if CONFIG_KPROBES is disabled:

arch/s390/kernel/uprobes.c:79:14:
 error: implicit declaration of function 'probe_get_fixup_type'
arch/s390/kernel/uprobes.c:87:14:
 error: 'FIXUP_PSW_NORMAL' undeclared (first use in this function)

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>