common: Move mii_init() function out of common.h

This function belongs in mii.h so move it over.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/cpu/armv8/fsl-layerscape/cpu.c b/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
index 59d03b1..374fde6 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
+++ b/arch/arm/cpu/armv8/fsl-layerscape/cpu.c
@@ -39,6 +39,7 @@
 #include <fsl_validate.h>
 #endif
 #endif
+#include <linux/mii.h>
 
 DECLARE_GLOBAL_DATA_PTR;