Blackfin: bf537-pnav: increase monitor len

Building this board for parallel flash fills up the bss section and thus
fails to link, so bump up the monitor size a bit.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

include/configs/bf537-pnav.h

@@ -51,7 +51,7 @@
 #define CONFIG_EBIU_AMBCTL0_VAL	0x7BB033B0
 #define CONFIG_EBIU_AMBCTL1_VAL	0xFFC27BB0
 
-#define CONFIG_SYS_MONITOR_LEN		(256 * 1024)
+#define CONFIG_SYS_MONITOR_LEN		(512 * 1024)
 #define CONFIG_SYS_MALLOC_LEN		(128 * 1024)