mfd: exynos-lpass: Describe driver in KConfig

Describe better which driver applies to which SoC, to make configuring
kernel for Samsung SoC easier.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210924133332.112092-1-krzysztof.kozlowski@canonical.com

drivers/mfd/Kconfig

@@ -417,7 +417,9 @@ config MFD_EXYNOS_LPASS
 	select REGMAP_MMIO
 	help
 	  Select this option to enable support for Samsung Exynos Low Power
-	  Audio Subsystem.
+	  Audio Subsystem present on some of Samsung Exynos
+	  SoCs (e.g. Exynos5433).
+	  Choose Y here only if you build for such Samsung SoC.
 
 config MFD_GATEWORKS_GSC
 	tristate "Gateworks System Controller"