i2c: npcm: Change the way of getting GCR regmap

Change the way of getting NPCM system manager reigster (GCR)
and still maintain the old mechanism as a fallback if getting
nuvoton,sys-mgr fails while working with the legacy devicetree
file.

Signed-off-by: Tali Perry <tali.perry1@gmail.com>
Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Author: TaliPerry

drivers/i2c/busses/i2c-npcm7xx.c

@@ -2229,11 +2229,12 @@ static void npcm_i2c_init_debugfs(struct platform_device *pdev,
 
 static int npcm_i2c_probe_bus(struct platform_device *pdev)
 {
-	struct npcm_i2c *bus;
-	struct i2c_adapter *adap;
-	struct clk *i2c_clk;
+	struct device_node *np = pdev->dev.of_node;
 	static struct regmap *gcr_regmap;
 	static struct regmap *clk_regmap;
+	struct i2c_adapter *adap;
+	struct npcm_i2c *bus;
+	struct clk *i2c_clk;
 	int irq;
 	int ret;
 
@@ -2250,7 +2251,10 @@ static int npcm_i2c_probe_bus(struct platform_device *pdev)
 		return PTR_ERR(i2c_clk);
 	bus->apb_clk = clk_get_rate(i2c_clk);
 
-	gcr_regmap = syscon_regmap_lookup_by_compatible("nuvoton,npcm750-gcr");
+	gcr_regmap = syscon_regmap_lookup_by_phandle(np, "nuvoton,sys-mgr");
+	if (IS_ERR(gcr_regmap))
+		gcr_regmap = syscon_regmap_lookup_by_compatible("nuvoton,npcm750-gcr");
+
 	if (IS_ERR(gcr_regmap))
 		return PTR_ERR(gcr_regmap);
 	regmap_write(gcr_regmap, NPCM_I2CSEGCTL, NPCM_I2CSEGCTL_INIT_VAL);