[U-Boot] rockchip: clk: rk3288: add clk_enable function and support USB HOST0/HSIC

[Philipp Tomsich]

> The generic ehci-driver (ehci-generic.c) will try to enable the clocks
> listed in the DTSI. If this fails (e.g. due to clk_enable not being
> implemented in a driver and -ENOSYS being returned by the clk-uclass),
> the driver will bail our and print an error message.
> 
> This implements a minimal clk_enable for the RK3288 and supports the
> clocks mandatory for the EHCI controllers; as these are enabled by
> default we simply return success.
> 
> Signed-off-by: Wadim Egorov <w.egorov at phytec.de>
> Acked-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> ---
>  drivers/clk/rockchip/clk_rk3288.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 

Reviewed-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>