[bsp][sam9260] Fix Keil compile error.

bsp/at91sam9260/platform/rt_low_level_keil.inc

@@ -30,5 +30,5 @@ IRQ_STK_SIZE EQU 1024
 FIQ_STK_SIZE EQU 1024
 SYS_STK_SIZE EQU 512
 ;/* vector table start should be 0x00000000 or 0xFFFF0000 */
-VECTOR_TABLE_START    0x00000000
+VECTOR_TABLE_START EQU  0x00000000
     END