clk: Add clk_resolve_parent_clk()

Add clk_resolve_parent_clk() to resolve parent clock udevice name
based on clock-names DT property. This is used in SoC clock drivers
to look up the clock name in clock tables, which matches a clock
name in DT clock-names property, and convert it into udevice name
which is used by U-Boot clock framework to look up parent clock in
e.g. clk_register() using uclass_get_device_by_name(UCLASS_CLK,
parent_name, &parent);

Signed-off-by: Marek Vasut <marex@denx.de>
diff --git a/include/clk.h b/include/clk.h
index 045e923..a6ef4e0 100644
--- a/include/clk.h
+++ b/include/clk.h
@@ -351,6 +351,15 @@
 }
 
 /**
+ * clk_resolve_parent_clk - Determine name of clock udevice based on clock-names
+ * @dev:	The client udevice.
+ * @name:	The name of the clock to look up.
+ *
+ * Return name of the clock udevice which represents clock with clock-names name.
+ */
+const char *clk_resolve_parent_clk(struct udevice *dev, const char *name);
+
+/**
  * enum clk_defaults_stage - What stage clk_set_defaults() is called at
  * @CLK_DEFAULTS_PRE: Called before probe. Setting of defaults for clocks owned
  *                    by this clock driver will be defered until after probing.