mfd: omap-usb-host: Actually update hostconfig

The helper functions omap_usbhs_rev1_hostconfig()
and omap_usbhs_rev2_hostconfig() don't write into
the hostconfig register. Make sure that we write
the return value into the hostconfig register.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>