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/nitrogen6dl2g_defconfig b/configs/nitrogen6dl2g_defconfig
index c50e79a..11bee9b 100644
--- a/configs/nitrogen6dl2g_defconfig
+++ b/configs/nitrogen6dl2g_defconfig
@@ -37,7 +37,7 @@
 CONFIG_ENV_IS_IN_SPI_FLASH=y
 CONFIG_USB_FUNCTION_FASTBOOT=y
 CONFIG_FASTBOOT_BUF_ADDR=0x12000000
-CONFIG_FSL_ESDHC_IMX=y
+CONFIG_FSL_USDHC=y
 CONFIG_SPI_FLASH=y
 CONFIG_SF_DEFAULT_MODE=0
 CONFIG_SF_DEFAULT_SPEED=25000000