usb: ohci-ep93xx: tidy up driver (*probe) and (*remove)

Merge the usb_hcd_ep93xx_probe() into ohci_hcd_ep93xx_drv_probe() and
the usb_hcd_ep93xx_remove() into ohci_hcd_ep93xx_drv_remove(). As Alan
Stern pointed out, there is no reason for them to be separate.

Also, as Alan Stern suggested, eliminate the ep93xx_start_hc() and
ep93xx_stop_hc() routines and simply call clk_enable() and clk_disable()
directly. The extra level of redirection does not add any clarity.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>