Add AHCI support to u-boot

Add AHCI support in u-boot, enable the sata disk controllers which
following the AHCI protocol.

Signed-off-by:Jason Jin<jason.jin@freescale.com>
diff --git a/common/cmd_scsi.c b/common/cmd_scsi.c
index e804861..cc08743 100644
--- a/common/cmd_scsi.c
+++ b/common/cmd_scsi.c
@@ -43,8 +43,13 @@
 #else
 #define SCSI_DEV_ID		CONFIG_SCSI_DEV_ID
 #endif
+#elif defined CONFIG_SATA_ULI5288
+
+#define SCSI_VEND_ID 0x10b9
+#define SCSI_DEV_ID  0x5288
+
 #else
-#error CONFIG_SCSI_SYM53C8XX must be defined
+#error no scsi device defined
 #endif