imx: mx6ulevk: add CONFIG_SPI_FLASH_STMICRO

Add CONFIG_SPI_FLASH_STMICRO to let qspi driver can detect the
qspi chips.
"
=> sf probe
SF: Detected N25Q256 with page size 256 Bytes, erase size 64 KiB, total 32 MiB
"

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Jagan Teki <jteki@openedev.com>
Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Stefano Babic <sbabic@denx.de>
1 file changed