treewide: Migrate CONFIG_FSL_ESDHC to Kconfig

Migrate the CONFIG_FSL_ESDHC option to Kconfig.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/configs/mx6slevk_defconfig b/configs/mx6slevk_defconfig
index a49e9cd..abc7788 100644
--- a/configs/mx6slevk_defconfig
+++ b/configs/mx6slevk_defconfig
@@ -32,6 +32,7 @@
 CONFIG_DM_GPIO=y
 CONFIG_DM_I2C=y
 CONFIG_DM_MMC=y
+CONFIG_FSL_ESDHC=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_STMICRO=y
 CONFIG_PHYLIB=y