ASoC: fsl/powerpc: don't rely on the cell-index property

ASoC: fsl/powerpc: don't rely on the cell-index property

Instead of using the 'cell-index' property in the I2C adapter node to
determine the adapter number, just query the i2c_adapter object directly.

Previously, the I2C nodes always appeared in cell-index order, so the
dynamic numbering coincided with the cell-index property.  With commit
23b7e935 ("powerpc/85xx: Rework P1022DS device tree"), the I2C nodes are
unintentionally reversed in the device tree, and so the machine driver
guesses the wrong I2C adapter number.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>