gpio: tegra_gpio: implement rfree operation

Releasing a GPIO on Tegra necessitates changing its configuration to SFIO
to activate its special function. Without this reconfiguration, the special
function will be unavailable.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
diff --git a/drivers/gpio/tegra_gpio.c b/drivers/gpio/tegra_gpio.c
index b83df35..3d1e188 100644
--- a/drivers/gpio/tegra_gpio.c
+++ b/drivers/gpio/tegra_gpio.c
@@ -248,6 +248,16 @@
 	return 0;
 }
 
+static int tegra_gpio_rfree(struct udevice *dev, unsigned int offset)
+{
+	struct tegra_port_info *state = dev_get_priv(dev);
+
+	/* Set the pin as a SFIO */
+	set_config(state->base_gpio + offset, CFG_SFIO);
+
+	return 0;
+}
+
 static const struct dm_gpio_ops gpio_tegra_ops = {
 	.direction_input	= tegra_gpio_direction_input,
 	.direction_output	= tegra_gpio_direction_output,
@@ -255,6 +265,7 @@
 	.set_value		= tegra_gpio_set_value,
 	.get_function		= tegra_gpio_get_function,
 	.xlate			= tegra_gpio_xlate,
+	.rfree			= tegra_gpio_rfree,
 };
 
 /*