rpi: increase SYS_BOOTM_LEN to 64M on ARM64

On AArch64, kernel images are not self-decompressing and easily exceed
the 8MB limit.

Signed-off-by: Laurent Bonnans <laurent.bonnans@here.com>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
diff --git a/include/configs/rpi.h b/include/configs/rpi.h
index 8473cec..77d2d54 100644
--- a/include/configs/rpi.h
+++ b/include/configs/rpi.h
@@ -55,6 +55,10 @@
 #define CONFIG_SYS_MEMTEST_END		0x00200000
 #define CONFIG_LOADADDR			0x00200000
 
+#ifdef CONFIG_ARM64
+#define CONFIG_SYS_BOOTM_LEN		SZ_64M
+#endif
+
 /* Devices */
 /* GPIO */
 #define CONFIG_BCM2835_GPIO