pinctrl: berlin: guard sub-directory with CONFIG_PINCTRL_BERLIN

CONFIG_PINCTRL_BERLIN is more suitable than CONFIG_ARCH_BERLIN
to guard the drivers/pinctrl/berlin/ directory.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Jisheng Zhang <jszhang@marvell.com>
Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>