USB: ftdi_sio: fix endianess of max packet size

The USB max packet size (always little-endian) was not being byte
swapped on big-endian systems.

Applicable since [USB: ftdi_sio: fix hi-speed device packet size calculation] approx 2.6.31

Signed-off-by: Michael Wileczka <mikewileczka@yahoo.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>