reset: Add of_reset_control_get_optional_exclusive()

Add optional variant of of_reset_control_get_exclusive(). If the
requested reset is not specified in the device tree, this function
returns NULL instead of an error.

Suggested-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20211112184413.4391-2-biju.das.jz@bp.renesas.com
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

Author: bijudas

include/linux/reset.h

@@ -454,6 +454,26 @@ static inline struct reset_control *of_reset_control_get_exclusive(
 	return __of_reset_control_get(node, id, 0, false, false, true);
 }
 
+/**
+ * of_reset_control_get_optional_exclusive - Lookup and obtain an optional exclusive
+ *                                           reference to a reset controller.
+ * @node: device to be reset by the controller
+ * @id: reset line name
+ *
+ * Optional variant of of_reset_control_get_exclusive(). If the requested reset
+ * is not specified in the device tree, this function returns NULL instead of
+ * an error.
+ *
+ * Returns a struct reset_control or IS_ERR() condition containing errno.
+ *
+ * Use of id names is optional.
+ */
+static inline struct reset_control *of_reset_control_get_optional_exclusive(
+				struct device_node *node, const char *id)
+{
+	return __of_reset_control_get(node, id, 0, false, true, true);
+}
+
 /**
  * of_reset_control_get_shared - Lookup and obtain a shared reference
  *                               to a reset controller.