arch: armv8: fsl-layerscape: export serdes config to environment

Exports the serdes configuration as an environment variable for LS gen 3
SoCs, so it can be used in u-boot command line.  It should particularly
be useful for applying Linux DT overlays for the given serdes
configuration.
This code is called from arch_misc_init and not from the existing
serdes_init function because it depends on U-Boot environment being set
up.

Signed-off-by: Alex Marginean <alexandru.marginean@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/arch/arm/cpu/armv8/fsl-layerscape/cpu.c b/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
index dce915a..b443894 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
+++ b/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
@@ -1632,3 +1632,17 @@
 
 	return 0;
 }
+
+#ifdef CONFIG_ARCH_MISC_INIT
+__weak int serdes_misc_init(void)
+{
+	return 0;
+}
+
+int arch_misc_init(void)
+{
+	serdes_misc_init();
+
+	return 0;
+}
+#endif