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>

arch/s390/include/asm/dis.h

@@ -40,6 +40,8 @@ static inline int insn_length(unsigned char code)
 	return ((((int) code + 64) >> 7) + 1) << 1;
 }
 
+struct pt_regs;
+
 void show_code(struct pt_regs *regs);
 void print_fn_code(unsigned char *code, unsigned long len);
 int insn_to_mnemonic(unsigned char *instruction, char *buf, unsigned int len);