configs: imx8mn_evk: drop unused SDHC macro

With SPL_DM_MMC and DM_MMC, the two macros not needed, drop it.
 #define CONFIG_SYS_FSL_USDHC_NUM       2
 #define CONFIG_SYS_FSL_ESDHC_ADDR      0

Reviewed-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/include/configs/imx8mn_evk.h b/include/configs/imx8mn_evk.h
index 142fc3e..f969314 100644
--- a/include/configs/imx8mn_evk.h
+++ b/include/configs/imx8mn_evk.h
@@ -77,9 +77,4 @@
 #define CONFIG_SYS_PBSIZE		(CONFIG_SYS_CBSIZE + \
 					sizeof(CONFIG_SYS_PROMPT) + 16)
 
-/* USDHC */
-
-#define CONFIG_SYS_FSL_USDHC_NUM	2
-#define CONFIG_SYS_FSL_ESDHC_ADDR	0
-
 #endif