mx6sxsabresd: Load the correct dtb for revA board

Currently only imx6sx-sdb.dtb is loaded, but if revA board is used the
correct dtb is imx6sx-sdb-reva.dtb, so make this possible.

While at it, remove an extra 'mmc dev'.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>

board/freescale/mx6sxsabresd/mx6sxsabresd.c

@@ -540,9 +540,23 @@ int board_init(void)
 	return 0;
 }
 
+static bool is_reva(void)
+{
+	return (nxp_board_rev() == 1);
+}
+
+int board_late_init(void)
+{
+#ifdef CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
+	if (is_reva())
+		env_set("board_rev", "REVA");
+#endif
+	return 0;
+}
+
 int checkboard(void)
 {
-	puts("Board: MX6SX SABRE SDB\n");
+	printf("Board: MX6SX SABRE SDB rev%c\n", nxp_board_rev_string());
 
 	return 0;
 }