pinctrl: mvebu: armada-{370,375}: normalize audio pins

This commit aligns the naming of the audio 'lrclk' pin accross Marvell
SoCs.

Since only the subname is changed, the DT backward compatibility is
not affected.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>