distro: use imply to enable DISTRO_DEFAULTS as SoC default

The default of DISTRO_DEFAULTS is messy.  Using the 'imply' keyword
is equivalent and cleaner.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/arch/arm/cpu/armv8/fsl-layerscape/Kconfig b/arch/arm/cpu/armv8/fsl-layerscape/Kconfig
index c4a96d4..7edc06d 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/Kconfig
+++ b/arch/arm/cpu/armv8/fsl-layerscape/Kconfig
@@ -167,6 +167,7 @@
 	select SYS_I2C_MXC_I2C2
 	select SYS_I2C_MXC_I2C3
 	select SYS_I2C_MXC_I2C4
+	imply DISTRO_DEFAULTS
 	imply PANIC_HANG
 
 config FSL_LSCH2