allwinner: common: add missing header

Some code in sunxi_common.c requires symbols defined in sunxi_private.h,
so add the header to that file.
It was included via another header before, but let's make this explicit.
Reported-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

plat/allwinner/common/sunxi_common.c

@@ -9,6 +9,8 @@
 #include <sunxi_def.h>
 #include <xlat_tables_v2.h>
 
+#include "sunxi_private.h"
+
 static mmap_region_t sunxi_mmap[PLATFORM_MMAP_REGIONS + 1] = {
 	MAP_REGION_FLAT(SUNXI_ROM_BASE, SUNXI_ROM_SIZE,
 			MT_MEMORY | MT_RO | MT_SECURE),