mfd: omap-usb-host: Remove TLL specific code from USB HS core driver

The TLL specific code such as channels clocks enable/disable,
initialization functions are removed from the USBHS core
driver. The hwmod of the usb tll is retrieved and omap device
build is performed to created the platform device for the
usb tll component.

Signed-off-by: Keshava Munegowda <keshava_mgowda@ti.com>
Reviewed-by: Partha Basak <parthab@india.ti.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>