s390/dis: Fix printing of the register numbers

Since commit b006f19b ("lib/vsprintf.c: handle invalid format
specifiers more robustly") I get errors like
[...]
Krnl Code: 00000000004e2410: c00400000000        brcl 0,4e2410
Please remove unsupported %r in format string
[    8.179483] ------------[ cut here ]------------
[    8.179484] WARNING: at lib/vsprintf.c:1781

Turns out that our disassembler relied on %r not being used as format
string. Let's do the proper escaping of our decode buffers.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/dis.c

@@ -2015,7 +2015,7 @@ void show_code(struct pt_regs *regs)
 			*ptr++ = '\t';
 		ptr += print_insn(ptr, code + start, addr);
 		start += opsize;
-		printk(buffer);
+		printk("%s", buffer);
 		ptr = buffer;
 		ptr += sprintf(ptr, "\n          ");
 		hops++;
@@ -2042,7 +2042,7 @@ void print_fn_code(unsigned char *code, unsigned long len)
 		ptr += print_insn(ptr, code, (unsigned long) code);
 		*ptr++ = '\n';
 		*ptr++ = 0;
-		printk(buffer);
+		printk("%s", buffer);
 		code += opsize;
 		len -= opsize;
 	}