ASoC: clarify that SND_SOC_IMX_SGTL5000 is the old driver

Both SND_SOC_IMX_SGTL5000 and SND_SOC_FSL_ASOC_CARD implement the
fsl,imx-audio-sgtl5000 compatible string, which is confusing. It took a
little research to find out that the latter is much newer and it is
supposed to be the preferred choice since several years.

Add a clarification note to avoid wasting time for future readers.
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Link: https://lore.kernel.org/r/20230303093410.357621-1-luca.ceresoli@bootlin.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/fsl/Kconfig

@@ -294,6 +294,10 @@ config SND_SOC_IMX_SGTL5000
 	  Say Y if you want to add support for SoC audio on an i.MX board with
 	  a sgtl5000 codec.
 
+	  Note that this is an old driver. Consider enabling
+	  SND_SOC_FSL_ASOC_CARD and SND_SOC_SGTL5000 to use the newer
+	  driver.
+
 config SND_SOC_IMX_SPDIF
 	tristate "SoC Audio support for i.MX boards with S/PDIF"
 	select SND_SOC_IMX_PCM_DMA