board: ls2080ardb: Add fsl_fdt_fixup_flash

IFC and QSPI are muxed on board. Add fsl_fdt_fixup_flash() to disable
IFC node in dts if QSPI is enabled, or disable QSPI node in dts if
otherwise.

Signed-off-by: Santan Kumar <santan.kumar@nxp.com>
Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>
[YS: Revise commit message]
Reviewed-by: York Sun <york.sun@nxp.com>