MIPS: loongson: common: Setup: add a missing include

Add a missing include to get rid of the following sparse warning:
warning: symbol 'plat_mem_setup' was not declared. Should it be static?
Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8530/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/loongson/common/setup.c

@@ -10,6 +10,7 @@
 #include <linux/module.h>
 
 #include <asm/wbflush.h>
+#include <asm/bootinfo.h>
 
 #include <loongson.h>