Blackfin: fix typo in TRAS define in mem_init.h header

We defined SDRAM_tRAS to TRAS_4, but then wrongly defined SDRAM_tRAS_num
to 3.
Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

arch/blackfin/include/asm/mem_init.h

@@ -59,7 +59,7 @@
 #define SDRAM_tRP       TRP_1
 #define SDRAM_tRP_num   1
 #define SDRAM_tRAS      TRAS_4
-#define SDRAM_tRAS_num  3
+#define SDRAM_tRAS_num  4
 #define SDRAM_tRCD      TRCD_1
 #define SDRAM_tWR       TWR_2
 #endif