dm: spi: Convert Freescale ESPI driver to driver model

dm: spi: Convert Freescale ESPI driver to driver model

Modify the Freescale ESPI driver to support the driver model.
Also resolved the following problems:

===================== WARNING ======================
This board does not use CONFIG_DM_SPI. Please update
the board before v2019.04 for no dm conversion
and v2019.07 for partially dm converted drivers.
Failure to update can lead to driver/board removal
See doc/driver-model/MIGRATION.txt for more info.
====================================================
===================== WARNING ======================
This board does not use CONFIG_DM_SPI_FLASH. Please update
the board to use CONFIG_SPI_FLASH before the v2019.07 release.
Failure to update by the deadline may result in board removal.
See doc/driver-model/MIGRATION.txt for more info.
====================================================

Signed-off-by: Chuanhua Han <chuanhua.han@nxp.com>
Signed-off-by: Xiaowei Bao <xiaowei.bao@nxp.com>
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>