pinctrl: mvebu: pinctrl-armada-37xx: Update documentation block for 'struct armada_37xx_pin_group'

Correct misspellings and provide missing entries.

Fixes the following W=1 kernel build warning(s):

 drivers/pinctrl/mvebu/pinctrl-armada-37xx.c:68: warning: Function parameter or member 'start_pin' not described in 'armada_37xx_pin_group'
 drivers/pinctrl/mvebu/pinctrl-armada-37xx.c:68: warning: Function parameter or member 'val' not described in 'armada_37xx_pin_group'
 drivers/pinctrl/mvebu/pinctrl-armada-37xx.c:68: warning: Function parameter or member 'extra_pin' not described in 'armada_37xx_pin_group'
 drivers/pinctrl/mvebu/pinctrl-armada-37xx.c:68: warning: Function parameter or member 'extra_npins' not described in 'armada_37xx_pin_group'
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Gregory Clement <gregory.clement@bootlin.com>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Link: https://lore.kernel.org/r/20200713144930.1034632-25-lee.jones@linaro.orgSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/mvebu/pinctrl-armada-37xx.c

@@ -45,13 +45,14 @@
  * The pins of a pinmux groups are composed of one or two groups of contiguous
  * pins.
  * @name:	Name of the pin group, used to lookup the group.
- * @start_pins:	Index of the first pin of the main range of pins belonging to
+ * @start_pin:	Index of the first pin of the main range of pins belonging to
  *		the group
  * @npins:	Number of pins included in the first range
  * @reg_mask:	Bit mask matching the group in the selection register
- * @extra_pins:	Index of the first pin of the optional second range of pins
+ * @val:	Value to write to the registers for a given function
+ * @extra_pin:	Index of the first pin of the optional second range of pins
  *		belonging to the group
- * @npins:	Number of pins included in the second optional range
+ * @extra_npins:Number of pins included in the second optional range
  * @funcs:	A list of pinmux functions that can be selected for this group.
  * @pins:	List of the pins included in the group
  */