pinctrl: sh-pfc: Validate pins/marks in pin groups at build time

Add a build-time check, to ensure the number of pins and pin marks in a
pin group matches.  This helps catching bugs early.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>