Since 16ccaf5b ("pinctrl: sh-pfc: Accept standard function, pins and
groups properties") renesas pfc drivers accept generic "function", "pins"
and "groups" properties.

This patch updates the silk device tree to use the generic properties.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>