ohci-platform: Add support for devicetree instantiation

Add support for ohci-platform instantiation from devicetree, including
optionally getting clks and a phy from devicetree, and enabling / disabling
those on power_on / off.

This should allow using ohci-platform from devicetree in various cases.
Specifically after this commit it can be used for the ohci controller found
on Allwinner sunxi SoCs.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>