clk: introduce enable_count

As what Linux Kernel 5.3.0 provides when enable/disable clk,
there is an enable_count in clk_core_disable/enable. Introduce
enable_count to track the clk enable/disable count when
clk_enable/disable for CCF. And Initialize enable_count to 0 when
register the clk.

And clk tree dump with enable_count will be supported, it will
be easy for us to check the clk status with enable_count

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 39b3087..1cf9987 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -40,6 +40,7 @@
 		return ret;
 	}
 
+	clk->enable_count = 0;
 	/* Store back pointer to clk from udevice */
 	clk->dev->uclass_priv = clk;