spl_nor.c: Support devicetree sizes different from 16k

The devicetrees for various platforms already exceed 16k. Add a define
CONFIG_SYS_FDT_SIZE to specify the FDT size, and set to 16k for the
two boards that define this CONFIG_SYS_FDT_BASE parameter. This
allows platforms with larger devicetree blobs to boot from NOR.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
diff --git a/include/configs/a3m071.h b/include/configs/a3m071.h
index 8f17dd1..ab2477c 100644
--- a/include/configs/a3m071.h
+++ b/include/configs/a3m071.h
@@ -334,6 +334,7 @@
 
 #define CONFIG_SYS_OS_BASE	0xfc200000
 #define CONFIG_SYS_FDT_BASE	0xfc1e0000
+#define CONFIG_SYS_FDT_SIZE	(16<<10)
 
 #define	CONFIG_EXTRA_ENV_SETTINGS					\
 	"netdev=eth0\0"							\