mx6ul_14x14_evk: Select CONFIG_FSL_QSPI

Select CONFIG_FSL_QSPI so that the SPI can be probed:

=> sf probe
SF: Detected N25Q256 with page size 256 Bytes, erase size 64 KiB, total 32 MiB

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>