USB: add Cypress c67x00 low level interface code

This patch adds the low level support code for the Cypress c67x00 family of
OTG controllers.  The low level code is responsible for register access and
implements the software protocol for communicating with the 16bit
microcontroller inside the c67x00 device.

Communication is done over the HPI interface (16bit SRAM-like parallel bus).

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>