MIPS: board.c: move extern declarations to u-boot-mips.h

This fixes some remaining checkpatch.pl warnings.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
diff --git a/include/common.h b/include/common.h
index 8564a65..ecfa6c4 100644
--- a/include/common.h
+++ b/include/common.h
@@ -355,6 +355,9 @@
 # include <asm/mach-types.h>
 # include <asm/u-boot-nds32.h>
 #endif /* CONFIG_NDS32 */
+#ifdef CONFIG_MIPS
+# include <asm/u-boot-mips.h>
+#endif /* CONFIG_MIPS */
 
 #ifdef CONFIG_AUTO_COMPLETE
 int env_complete(char *var, int maxv, char *cmdv[], int maxsz, char *buf);