mpc52xx: Get rid of board-specific #ifdef's in cpu/mpc5xxx/ide.c

Total5200 and digsy MTC use I2C port 2 pins as a ATA chip select.
To avoid adding board-specific ifdefs to cpu/mpc5xxx/ide.c new
define CONFIG_SYS_ATA_CS_ON_I2C2 was introduced. It is used by
Total5200 and will be used by digsy MTC and other boards with
ATA CS on I2C pins.

Signed-off-by: Grzegorz Bernacki <gjb@semihalf.com>
diff --git a/include/configs/Total5200.h b/include/configs/Total5200.h
index 9a75848..1daa574 100644
--- a/include/configs/Total5200.h
+++ b/include/configs/Total5200.h
@@ -397,6 +397,7 @@
 #define	CONFIG_IDE_RESET		/* reset for ide supported	*/
 #define CONFIG_IDE_PREINIT
 
+#define CONFIG_SYS_ATA_CS_ON_I2C2
 #define CONFIG_SYS_IDE_MAXBUS		1	/* max. 1 IDE bus		*/
 #define CONFIG_SYS_IDE_MAXDEVICE	1	/* max. 1 drive per IDE bus	*/