usbfs: Increase arbitrary limit for USB 3 isopkt length

Increase the current arbitrary limit for isocronous packet size to a
value large enough to account for USB 3.0 super bandwidth streams,
bMaxBurst (0~15 allowed, 1~16 packets)
bmAttributes (bit 1:0, mult 0~2, 1~3 packets)
so the size max for one USB 3 isocronous transfer is
1024 byte * 16 * 3 = 49152 byte

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Federico Manzan <f.manzan@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>