i2c: fsl: Add option to get clock from DT

Add an option to get the clock speed from the device tree, hence adding
compatibility with DM clock drivers.

Signed-off-by: Mario Six <mario.six@gdsys.cc>

drivers/i2c/fsl_i2c.c

@@ -12,6 +12,7 @@
 #include <i2c.h>		/* Functional interface */
 #include <asm/io.h>
 #include <asm/fsl_i2c.h>	/* HW definitions */
+#include <clk.h>
 #include <dm.h>
 #include <mapmem.h>
 
@@ -573,6 +574,7 @@ static int fsl_i2c_set_bus_speed(struct udevice *bus, uint speed)
 static int fsl_i2c_ofdata_to_platdata(struct udevice *bus)
 {
 	struct fsl_i2c_dev *dev = dev_get_priv(bus);
+	struct clk clock;
 
 	dev->base = map_sysmem(dev_read_addr(bus), sizeof(struct fsl_i2c_base));
 
@@ -584,7 +586,11 @@ static int fsl_i2c_ofdata_to_platdata(struct udevice *bus)
 					     0x7f);
 	dev->speed = dev_read_u32_default(bus, "clock-frequency", 400000);
 
-	dev->i2c_clk = dev->index ? gd->arch.i2c2_clk : gd->arch.i2c1_clk;
+	if (!clk_get_by_index(bus, 0, &clock))
+		dev->i2c_clk = clk_get_rate(&clock);
+	else
+		dev->i2c_clk = dev->index ? gd->arch.i2c2_clk :
+					    gd->arch.i2c1_clk;
 
 	return 0;
 }