Following the file renaming to use the "usb_dwc" prefix, this commit
updates the symbol names of those files to use the "usb_dwc" as well.
Some LL functions were also renamed so that the register name is
mentioned.
This commit updates the DWC_OTG based struct/ll/hal file names to
use the prefix "usb_dwc". This naming scheme reduces ambiguity if
another USB controller implementation is added.
As a result, "hcd.c" has been renamed to "hcd_dwc.c"
morris