pico: Convert to CONFIG_FSL_USDHC

The eSDHC config symbol has been converted to CONFIG_FSL_USDHC, so
adjust it accordingly in order to fix the build errors:

https://travis-ci.org/sbabic/u-boot-imx/jobs/584781580#L1287Reported-by: NAnatolij Gustschin <agust@denx.de>
Signed-off-by: NFabio Estevam <festevam@gmail.com>

configs/pico-dwarf-imx6ul_defconfig

@@ -44,7 +44,7 @@ CONFIG_FASTBOOT_CMD_OEM_FORMAT=y
 CONFIG_DM_GPIO=y
 CONFIG_DM_I2C=y
 CONFIG_DM_MMC=y
-CONFIG_FSL_ESDHC=y
+CONFIG_FSL_USDHC=y
 CONFIG_PHYLIB=y
 CONFIG_PHY_MICREL=y
 CONFIG_MII=y

configs/pico-dwarf-imx7d_defconfig

@@ -52,7 +52,7 @@ CONFIG_FASTBOOT_CMD_OEM_FORMAT=y
 CONFIG_DM_GPIO=y
 CONFIG_DM_MMC=y
 CONFIG_SUPPORT_EMMC_BOOT=y
-CONFIG_FSL_ESDHC=y
+CONFIG_FSL_USDHC=y
 CONFIG_PHYLIB=y
 CONFIG_MII=y
 CONFIG_PINCTRL=y

configs/pico-nymph-imx7d_defconfig

@@ -52,7 +52,7 @@ CONFIG_FASTBOOT_CMD_OEM_FORMAT=y
 CONFIG_DM_GPIO=y
 CONFIG_DM_MMC=y
 CONFIG_SUPPORT_EMMC_BOOT=y
-CONFIG_FSL_ESDHC=y
+CONFIG_FSL_USDHC=y
 CONFIG_PHYLIB=y
 CONFIG_MII=y
 CONFIG_PINCTRL=y