sh: shx3: pinmux: Use driver-provided pinmux info

Pinmux info for the sh machines is now provided by pinmux drivers.
Remove the duplicate copy in arch code.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>