USB: EHCI: define extension registers like normal ones

This patch (as1562) cleans up the definitions of the EHCI extended
registers to be consistent with the definitions of the standard
registers.  This makes the code look a lot nicer, with no functional
change.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>