Fix usb_serial_probe() problem introduced by the recent kfifo changes

The USB serial code was a new user of the kfifo API, and it was missed
when porting things to the new kfifo API.

Please make the write_fifo in place.  Here is my patch to fix the
regression and full ported version.

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Reported-and-tested-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Greg KH <greg@kroah.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
index acf6e45..1819396 100644
--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -16,6 +16,7 @@
 #include <linux/kref.h>
 #include <linux/mutex.h>
 #include <linux/sysrq.h>
+#include <linux/kfifo.h>
 
 #define SERIAL_TTY_MAJOR	188	/* Nice legal number now */
 #define SERIAL_TTY_MINORS	254	/* loads of devices :) */
@@ -94,7 +95,7 @@
 	unsigned char		*bulk_out_buffer;
 	int			bulk_out_size;
 	struct urb		*write_urb;
-	struct kfifo		*write_fifo;
+	struct kfifo		write_fifo;
 	int			write_urb_busy;
 	__u8			bulk_out_endpointAddress;