imx: imx8mm-beacon: Enable FlexSPI in U-Boot

In order to use the FlexSPI interface in U-Boot, configure
the alias to make spi0 point to flexspi.

With that enabled, sf probe detects the QSPI part as:
SF: Detected n25q256ax1 with page size 256 Bytes, erase size 4 KiB, total 32 MiB

Signed-off-by: Adam Ford <aford173@gmail.com>
1 file changed