sbc8641: remove unused OF_FLAT_TREE_MAX_SIZE

this had slipped through the cracks, since the sbc board was added
after I wrote the original patch to remove all these symbols, and
before it was merged.
Signed-off-by: NKim Phillips <kim.phillips@freescale.com>

include/configs/sbc8641d.h

@@ -270,9 +270,6 @@
 #define CONFIG_OF_FLAT_TREE	1
 #define CONFIG_OF_BOARD_SETUP	1
 
-/* maximum size of the flat tree (8K) */
-#define OF_FLAT_TREE_MAX_SIZE	8192
-
 #define OF_CPU		"PowerPC,8641@0"
 #define OF_SOC		"soc@f8000000"
 #define OF_TBCLK	(bd->bi_busfreq / 4)