pinctrl: sh-pfc: Add SH_PFC_PIN_CFG_PULL_UP_DOWN shorthand

It is very common for a pin to support both pull-up and pull-down
functionality.  Hence add a shorthand SH_PFC_PIN_CFG_PULL_UP_DOWN.
This not only reduces typing, but also avoids the need for several line
breaks, and makes many overly long lines shorter, improving
readability.

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