clk: Fix clk_set_parent() regression

The commit ac30d90f33 ("clk: Ensure the parent clocks are enabled
while reparenting") add a call to clk_enable() for the parent clock.

For clock drivers that do not implement the enable() ops, like most
Rockchip clock drivers, this now cause the set_parent() ops to never
be called when CLK_CCF=n (default for Rockchip).

clk_enable() typically return -ENOSYS when the enable() ops is not
implemented by the clock driver, with CLK_CCF=y clk_enable() instead
return 0 when the enable() ops is unimplemented.

Change to ignore -ENOSYS from the newly introduced clk_enable() call to
fix this regression and restore the old behavior of set_parent() ops
being called regardless of if enable() ops is implemented or not.

Fixes: ac30d90f33 ("clk: Ensure the parent clocks are enabled while reparenting")
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Tested-by: Dang Huynh <danct12@riseup.net>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/clk/clk-uclass.c

@@ -627,7 +627,7 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
 		return -ENOSYS;
 
 	ret = clk_enable(parent);
-	if (ret) {
+	if (ret && ret != -ENOSYS) {
 		printf("Cannot enable parent %s\n", parent->dev->name);
 		return ret;
 	}