usb: musb: abstract out ULPI_BUSCONTROL register reads/writes

The USB PHY on current Blackfin processors is a UTMI+ level 2 PHY.
However, it has no ULPI support - so there are no registers at all.
That means accesses to ULPI_BUSCONTROL have to be abstracted away
like other MUSB registers.

This fixes building for Blackfin parts again.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: Anand Gadiyar <gadiyar@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>