USB: mos7840: fix pointer casts

Silence compiler warnings on 64-bit systems introduced by commit
05cf0dec ("USB: mos7840: fix race in led handling") which uses the
usb-serial data pointer to temporarily store the device type during
probe but failed to add the required casts.

[gregkh - change uintptr_t to unsigned long]

Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>