of: property: Add device link support for pinctrl-0 through pinctrl-8

Add support for pinctrl-0 through pinctrl-8 explicitly instead of trying
to add support for pinctrl-%d properties.

Of all the pinctrl-* properties in dts files (20322), only 47% (9531)
are pinctrl-%d properties. Of all the pinctrl-%d properties, 99.5%
(9486) are made up of pinctrl-[0-2]. 'pinctrl-8' is the current maximum
found in dts files.

Trying to parse all pinctrl-* properties and checking for pinctrl-%d is
unnecessarily complicated. So, just add support for pinctrl-[0-8] for
now. In the unlikely event we ever exceed pinctrl-8, we can come back
and improve this.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20200724234415.1651639-2-saravanak@google.com
Signed-off-by: Rob Herring <robh@kernel.org>