malta: set CONFIG_SYS_BOOTM_LEN to 64MB

Allow a larger kernel binary to be decompressed - the default 8MB can
become limiting on a Malta.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>

include/configs/malta.h

@@ -54,6 +54,7 @@
 
 #define CONFIG_SYS_MALLOC_LEN		(128 * 1024)
 #define CONFIG_SYS_BOOTPARAMS_LEN	(128 * 1024)
+#define CONFIG_SYS_BOOTM_LEN		(64 * 1024 * 1024)
 
 /*
  * Console configuration