sgtl5000 codec needs MCLK clock to be present so that it can
successfully read/write via I2C.

In the case of wandboard, MCLK is provided via
MX6QDL_PAD_GPIO_0__CCM_CLKO1 pad.

Move the MCLK pinctrl from hog group to the codec group, so that the
codec clock can be present prior to reading the codec ID.

This avoids the following error that happens from time to time:

[    2.484443] sgtl5000 1-000a: Error reading chip id -6
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>