arm64: defconfig: Enable flash device drivers for QorIQ boards

Enable the flash devices used on NXP/FSL QorIQ reference boards
supported in mainline kernel.  Drivers are enabled as built-in for RFS
access without initramfs.

Signed-off-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>