pinctrl: mvebu: Fix dove_audio1_ctrl_set function

When setting audio1 pinmux the bits in the corresponding registers
are not cleared. This fix first clears all bits and then sets the
required bits according to the selected function.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>