pinctrl: armada-37xx: Remove unused macro PIN_GRP()

Macro PIN_GRP() is not used, remove it.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20220805122202.23174-4-pali@kernel.org


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>