rockchip: clk: rk3288: add clk_enable function and support USB HOST0/HSIC

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@phytec.de>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

drivers/clk/rockchip/clk_rk3288.c

@@ -893,12 +893,25 @@ static int __maybe_unused rk3288_clk_set_parent(struct clk *clk, struct clk *par
 	return -ENOENT;
 }
 
+static int rk3288_clk_enable(struct clk *clk)
+{
+	switch (clk->id) {
+	case HCLK_USBHOST0:
+	case HCLK_HSIC:
+		return 0;
+	}
+
+	debug("%s: unsupported clk %ld\n", __func__, clk->id);
+	return -ENOENT;
+}
+
 static struct clk_ops rk3288_clk_ops = {
 	.get_rate	= rk3288_clk_get_rate,
 	.set_rate	= rk3288_clk_set_rate,
 #if CONFIG_IS_ENABLED(OF_CONTROL) && !CONFIG_IS_ENABLED(OF_PLATDATA)
 	.set_parent	= rk3288_clk_set_parent,
 #endif
+	.enable = rk3288_clk_enable,
 };
 
 static int rk3288_clk_ofdata_to_platdata(struct udevice *dev)