ARM: dts: imx6qdl-colibri: Fix audio channel swap

When running a stress playback/stop loop test on a mx6colibri channel
swaps can be noticed randomly.

Increasing the SGTL5000 LRCLK pad strength to its maximum value fixes
the issue, so add the 'lrclk-strength' property to avoid the audio
channel swaps.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>