dm: gpio: Rename set_dir_flags() method to update_flags()

The current method is a misnomer since it is also used (e.g. by stm32) to
update pull settings and open source/open drain.

Rename it and expand the documentation to cover a few more details.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>

Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/drivers/pinctrl/pinctrl-stmfx.c b/drivers/pinctrl/pinctrl-stmfx.c
index 1a8d0a3..6147e86 100644
--- a/drivers/pinctrl/pinctrl-stmfx.c
+++ b/drivers/pinctrl/pinctrl-stmfx.c
@@ -163,8 +163,8 @@
 	return stmfx_write_reg(dev, STMFX_REG_GPIO_DIR, offset, 1);
 }
 
-static int stmfx_gpio_set_dir_flags(struct udevice *dev, unsigned int offset,
-				    ulong flags)
+static int stmfx_gpio_set_flags(struct udevice *dev, unsigned int offset,
+				ulong flags)
 {
 	int ret = -ENOTSUPP;
 
@@ -266,7 +266,7 @@
 	.get_function = stmfx_gpio_get_function,
 	.direction_input = stmfx_gpio_direction_input,
 	.direction_output = stmfx_gpio_direction_output,
-	.set_dir_flags = stmfx_gpio_set_dir_flags,
+	.set_flags = stmfx_gpio_set_flags,
 	.get_dir_flags = stmfx_gpio_get_dir_flags,
 };