lib/vsprintf: Do not handle %pO[^F] as %px

This patch avoids that gcc reports the following when building with W=1:

lib/vsprintf.c:1941:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   switch (fmt[1]) {
   ^~~~~~

Fixes: 7b1924a1d9 ("vsprintf: add printk specifier %px")
Link: http://lkml.kernel.org/r/[email protected]
Cc: [email protected]
Cc: Bart Van Assche <[email protected]>
Cc: Pantelis Antoniou <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: v4.15+ <[email protected]>
Signed-off-by: Bart Van Assche <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>

lib/vsprintf.c

@@ -1942,6 +1942,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 		case 'F':
 			return device_node_string(buf, end, ptr, spec, fmt + 1);
 		}
+		break;
 	case 'x':
 		return pointer_string(buf, end, ptr, spec);
 	}