fsl-asoc-card machine driver also supports sgtl5000, so use it favor
of the imx-sgtl5000 machine driver, which will be probably be removed
in the future.

Tested on a imx25-pdk board.
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>