Convert CONFIG_FSL_ESDHC_PIN_MUX to Kconfig

This converts the following to Kconfig:
   CONFIG_FSL_ESDHC_PIN_MUX

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/MPC837XERDB_defconfig b/configs/MPC837XERDB_defconfig
index 40fc1d1..a227ca8 100644
--- a/configs/MPC837XERDB_defconfig
+++ b/configs/MPC837XERDB_defconfig
@@ -195,6 +195,7 @@
 CONFIG_SYS_I2C_SLAVE=0x7F
 CONFIG_SYS_I2C_SPEED=400000
 CONFIG_FSL_ESDHC=y
+CONFIG_FSL_ESDHC_PIN_MUX=y
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_FLASH_CFI_DRIVER=y
 CONFIG_FLASH_SHOW_PROGRESS=0