pico-imx6ul: Remove CONFIG_FSL_USDHC from .h

The CONFIG_FSL_USDHC is defined inside "mx6_common.h", which is
already included in this file.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
diff --git a/include/configs/pico-imx6ul.h b/include/configs/pico-imx6ul.h
index 535f0b2..ead242d 100644
--- a/include/configs/pico-imx6ul.h
+++ b/include/configs/pico-imx6ul.h
@@ -28,7 +28,6 @@
 #define CONFIG_MXC_UART_BASE		UART6_BASE_ADDR
 
 /* MMC Configs */
-#define CONFIG_FSL_USDHC
 #define CONFIG_SYS_FSL_ESDHC_ADDR	USDHC1_BASE_ADDR
 #define CONFIG_SUPPORT_EMMC_BOOT