clk: Rename clk_get_by_driver_info()

This is actually a misnomer now, since the phandle info may contain
a driver_info index or a udevice index. Rename it to use the word
'phandle', which seems more accurate. Add a comment while we are here.

Also add a test for this function.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/mmc/ftsdc010_mci.c b/drivers/mmc/ftsdc010_mci.c
index b8cafeb..570d54c 100644
--- a/drivers/mmc/ftsdc010_mci.c
+++ b/drivers/mmc/ftsdc010_mci.c
@@ -433,7 +433,7 @@
 	chip->priv = dev;
 	chip->dev_index = 1;
 	memcpy(priv->minmax, dtplat->clock_freq_min_max, sizeof(priv->minmax));
-	ret = clk_get_by_driver_info(dev, dtplat->clocks, &priv->clk);
+	ret = clk_get_by_phandle(dev, dtplat->clocks, &priv->clk);
 	if (ret < 0)
 		return ret;
 #endif
diff --git a/drivers/mmc/rockchip_dw_mmc.c b/drivers/mmc/rockchip_dw_mmc.c
index 855c0e7..7f8dea1 100644
--- a/drivers/mmc/rockchip_dw_mmc.c
+++ b/drivers/mmc/rockchip_dw_mmc.c
@@ -123,7 +123,7 @@
 	priv->minmax[0] = 400000;  /*  400 kHz */
 	priv->minmax[1] = dtplat->max_frequency;
 
-	ret = clk_get_by_driver_info(dev, dtplat->clocks, &priv->clk);
+	ret = clk_get_by_phandle(dev, dtplat->clocks, &priv->clk);
 	if (ret < 0)
 		return ret;
 #else