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/platinum_picon_defconfig b/configs/platinum_picon_defconfig
index 4cc4954..886ddac 100644
--- a/configs/platinum_picon_defconfig
+++ b/configs/platinum_picon_defconfig
@@ -48,7 +48,7 @@
 CONFIG_MTDPARTS_DEFAULT="mtdparts=gpmi-nand:14M(spl),2M(uboot),512k(env1),512k(env2),495M(ubi0),14M(res0),2M(res1),512k(res2),512k(res3),-(ubi1)"
 CONFIG_CMD_UBI=y
 CONFIG_ENV_IS_IN_NAND=y
-CONFIG_FSL_ESDHC_IMX=y
+CONFIG_FSL_USDHC=y
 CONFIG_NAND=y
 CONFIG_NAND_MXS=y
 CONFIG_PHYLIB=y