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/riotboard_spl_defconfig b/configs/riotboard_spl_defconfig
index 427bd9d..cf3647a 100644
--- a/configs/riotboard_spl_defconfig
+++ b/configs/riotboard_spl_defconfig
@@ -32,7 +32,7 @@
 CONFIG_ENV_IS_IN_MMC=y
 CONFIG_DM=y
 CONFIG_SUPPORT_EMMC_BOOT=y
-CONFIG_FSL_ESDHC_IMX=y
+CONFIG_FSL_USDHC=y
 CONFIG_SPI_FLASH=y
 CONFIG_SF_DEFAULT_MODE=0
 CONFIG_SF_DEFAULT_SPEED=20000000