When David added an entry to the gadget_chips.h file for the dummy_hcd
driver, he mistakenly used the name "dummy_udc" rather than "dummy_hcd".
The mistake is understandable, since other controllers use "_udc" in their
names and it is illogical to put "_hcd" in a _device_ controller's name.

This patch updates the dummy_hcd driver and changes the gadget name to
agree with the gadget_chips.h entry.