clk: convert API to match reset/mailbox style

The following changes are made to the clock API:
* The concept of "clocks" and "peripheral clocks" are unified; each clock
  provider now implements a single set of clocks. This provides a simpler
  conceptual interface to clients, and better aligns with device tree
  clock bindings.
* Clocks are now identified with a single "struct clk", rather than
  requiring clients to store the clock provider device and clock identity
  values separately. For simple clock consumers, this isolates clients
  from internal details of the clock API.
* clk.h is split so it only contains the client/consumer API, whereas
  clk-uclass.h contains the provider API. This aligns with the recently
  added reset and mailbox APIs.
* clk_ops .of_xlate(), .request(), and .free() are added so providers
  can customize these operations if needed. This also aligns with the
  recently added reset and mailbox APIs.
* clk_disable() is added.
* All users of the current clock APIs are updated.
* Sandbox clock tests are updated to exercise clock lookup via DT, and
  clock enable/disable.
* rkclk_get_clk() is removed and replaced with standard APIs.

Buildman shows no clock-related errors for any board for which buildman
can download a toolchain.

test/py passes for sandbox (which invokes the dm clk test amongst
others).

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/clk/clk_fixed_rate.c b/drivers/clk/clk_fixed_rate.c
index 8beda9c..797e537 100644
--- a/drivers/clk/clk_fixed_rate.c
+++ b/drivers/clk/clk_fixed_rate.c
@@ -5,7 +5,7 @@
  */
 
 #include <common.h>
-#include <clk.h>
+#include <clk-uclass.h>
 #include <dm/device.h>
 
 DECLARE_GLOBAL_DATA_PTR;
@@ -16,19 +16,16 @@
 
 #define to_clk_fixed_rate(dev)	((struct clk_fixed_rate *)dev_get_platdata(dev))
 
-static ulong clk_fixed_rate_get_rate(struct udevice *dev)
+static ulong clk_fixed_rate_get_rate(struct clk *clk)
 {
-	return to_clk_fixed_rate(dev)->fixed_rate;
-}
+	if (clk->id != 0)
+		return -EINVAL;
 
-static ulong clk_fixed_rate_get_periph_rate(struct udevice *dev, int periph)
-{
-	return clk_fixed_rate_get_rate(dev);
+	return to_clk_fixed_rate(clk->dev)->fixed_rate;
 }
 
 const struct clk_ops clk_fixed_rate_ops = {
 	.get_rate = clk_fixed_rate_get_rate,
-	.get_periph_rate = clk_fixed_rate_get_periph_rate,
 };
 
 static int clk_fixed_rate_ofdata_to_platdata(struct udevice *dev)