Convert CONFIG_FSL_USDHC to Kconfig

This converts the following to Kconfig:
   CONFIG_FSL_USDHC

Signed-off-by: Adam Ford <aford173@gmail.com>
[trini: Add IMX8M, TARGET_S32V234EVB to FSL_USDHC list]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/warp7_defconfig b/configs/warp7_defconfig
index 11f16cf..a022454 100644
--- a/configs/warp7_defconfig
+++ b/configs/warp7_defconfig
@@ -39,7 +39,7 @@
 CONFIG_DM_I2C=y
 CONFIG_DM_MMC=y
 CONFIG_SUPPORT_EMMC_BOOT=y
-CONFIG_FSL_ESDHC_IMX=y
+CONFIG_FSL_USDHC=y
 CONFIG_PINCTRL=y
 CONFIG_PINCTRL_IMX7=y
 CONFIG_DM_PMIC=y