implement overrides for spl_spi_boot_bus() and spl_spi_boot_cs() lookup functions according to bootmode selection, so as to support both QSPI and OSPI boot using the same build. Signed-off-by: Vaishnav Achath <vaishnav.a@ti.com> Reviewed-by: Pratyush Yadav <p.yadav@ti.com>