i2c: mv64xxx: Fix reset controller handling

The reset framework recently gained optional stubs when CONFIG_RESET_CONTROLLER
is not selected. It also introduced a function reset_get_optional, that is also
dummy-defined whenever the framework isn't enabled, for drivers that needs an
optional reset controller.

Switch to this function, since the mv64xxx driver is in this case. This also
fixes a compilation breakage whenever the reset framework wasn't selected:

drivers/i2c/busses/i2c-mv64xxx.c:771:2: error: implicit declaration of function 'devm_reset_control_get'

While we're at it, remove the redundant test on dev.of_node surrounding the
calls to reset framework functions, since it will either be a valid pointer, an
error pointer in the case where we called reset_get_optional without an of_node
pointer or if it failed, or NULL if we're not loaded through DT.
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-mv64xxx.c

@@ -757,7 +757,7 @@ mv64xxx_of_config(struct mv64xxx_i2c_data *drv_data,
 	}
 	drv_data->irq = irq_of_parse_and_map(np, 0);
 
-	drv_data->rstc = devm_reset_control_get(dev, NULL);
+	drv_data->rstc = devm_reset_control_get_optional(dev, NULL);
 	if (IS_ERR(drv_data->rstc)) {
 		if (PTR_ERR(drv_data->rstc) == -EPROBE_DEFER) {
 			rc = -EPROBE_DEFER;
@@ -889,7 +889,7 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 exit_free_irq:
 	free_irq(drv_data->irq, drv_data);
 exit_reset:
-	if (pd->dev.of_node && !IS_ERR(drv_data->rstc))
+	if (!IS_ERR_OR_NULL(drv_data->rstc))
 		reset_control_assert(drv_data->rstc);
 exit_clk:
 #if defined(CONFIG_HAVE_CLK)
@@ -909,7 +909,7 @@ mv64xxx_i2c_remove(struct platform_device *dev)
 
 	i2c_del_adapter(&drv_data->adapter);
 	free_irq(drv_data->irq, drv_data);
-	if (dev->dev.of_node && !IS_ERR(drv_data->rstc))
+	if (!IS_ERR_OR_NULL(drv_data->rstc))
 		reset_control_assert(drv_data->rstc);
 #if defined(CONFIG_HAVE_CLK)
 	/* Not all platforms have a clk */