configs: mx6sxsabresd: drop CONFIG_SYS_FSL_USDHC_NUM

With DM_MMC, CONFIG_SYS_FSL_USDHC_NUM is not needed.

Reviewed-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/include/configs/mx6sxsabresd.h b/include/configs/mx6sxsabresd.h
index b679d13..2552fc0 100644
--- a/include/configs/mx6sxsabresd.h
+++ b/include/configs/mx6sxsabresd.h
@@ -149,6 +149,4 @@
 #endif
 #endif
 
-#define CONFIG_SYS_FSL_USDHC_NUM	3
-
 #endif				/* __CONFIG_H */