Blackfin: bf52x/bf54x: fix up usb MMR defines

The bf52x/bf54x have the incorrect addresses for USB_EP_NI7_RXINTERVAL
and USB_EP_NI7_TXCOUNT, so adjust those.

Further, the bf54x header puts the USB defines in the wrong place, so
shuffle them back to the right grouping.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>