Add some bare-bones support for enabling usb and usbphy clocks.  This
is temporary code to keep imx development moving forward for now.  In
the long run we need a SoC-independant clock management API.
Add a "no-op" USB PHY driver for imx-family SoCs.  This is used when the
phy clocks need to be enabled, but no other hardware setup is needed to
make the phy work.
Sponsored by:	The FreeBSD Foundation
Revert r257385; was testing a shell script to automatically append the proper
"Sponsored by" and failed at error handling.

Sponsored by:	The FreeBSD Foundation