USB: ftdi_sio: fix oops due to processing workarounds too early

Fix an oops that happens in relation with applying work arounds for buggy
ftdi_sio devices.  The quirks were handled too early because due to changes in
the initialisation of usb serial devices the device was not fully initialised
when the old hook was called.

Addresses bug 8564

Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>