Blackfin: bf548-ezkit: bump SPI flash size up

The current size used (256KiB) is smaller than the LDR created for
the bf548-ezkit, so 'run update' doesn't work correctly.  So bump
up the size a bit by making this flexible per-board config.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/include/configs/bf548-ezkit.h b/include/configs/bf548-ezkit.h
index d299dc1..4412177 100644
--- a/include/configs/bf548-ezkit.h
+++ b/include/configs/bf548-ezkit.h
@@ -182,6 +182,7 @@
 #define CONFIG_BOARD_EARLY_INIT_F
 #define CONFIG_RTC_BFIN
 #define CONFIG_UART_CONSOLE	1
+#define CONFIG_BFIN_SPI_IMG_SIZE 0x50000
 
 #ifndef __ADSPBF542__
 /* Don't waste time transferring a logo over the UART */