USB: pxa27x_udc: use four bits to store endpoint addresses

Endpoint addresses on pxa27x can be programmed as 1-15, but since
only three bits were being used to store the endpoint number it
was possible to overflow.

Signed-off-by: Matt Reimer <mreimer@sdgsystems.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>