imx: mx6slevk: enable DM_SPI and DM_SPI_FLASH

With DM_SPI and DM_SPI_FLASH enabled, we could get:

spi          0  [   ]   mxc_spi               |   |   |   `-- ecspi@02008000
spi_flash    0  [   ]   spi_flash_std         |   |   |       `-- m25p80@0

Signed-off-by: Peng Fan <peng.fan@nxp.com>
4 files changed