pinctrl/meson: fix typo in PDM's pin name

Other pins have _a or _x suffix, but this one doesn't have any. Most
likely this is a typo.

Fixes: dabad1ff

 ("pinctrl: meson: add pinctrl driver support for Meson-A1 SoC")
Signed-off-by: Jan Dakinevich <jan.dakinevich@salutedevices.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Message-ID: <20240325113058.248022-1-jan.dakinevich@salutedevices.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>