USB: dummy-hcd: fix connection failures (wrong speed)

The dummy-hcd UDC driver is not careful about the way it handles
connection speeds.  It ignores the module parameter that is supposed
to govern the maximum connection speed and it doesn't set the HCD
flags properly for the case where it ends up running at full speed.

The result is that in many cases, gadget enumeration over dummy-hcd
fails because the bMaxPacketSize byte in the device descriptor is set
incorrectly.  For example, the default settings call for a high-speed
connection, but the maxpacket value for ep0 ends up being set for a
Super-Speed connection.

This patch fixes the problem by initializing the gadget's max_speed
and the HCD flags correctly.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: <stable@vger.kernel.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>