ARM: dts: imx: specify the value of audmux pinctrl instead of 0x80000000

We must specify the value of audmux pinctrl if we want to use pinctrl_pm().
Thus change bypass value 0x80000000 to what we exactly need.

This patch also seperately unset PUE bit for TXD so that IOMUX won't pull
up/down the pin after turning into tristate. When we use SSI normal mode to
playback monaural audio via I2S signal, there'd be a pulled curve occur to
its signal at the second slot if setting PUE bit for TXD. And it will make
the second channel to play a constant noise. So by keeping the signal level
in the second slot, we can get a constant high level signal (-1) or a low
level one (0).

Signed-off-by: Nicolin Chen <b42378@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>