arm64: dts: renesas: rzg2ul-smarc-som: Enable serial NOR flash

arm64: dts: renesas: rzg2ul-smarc-som: Enable serial NOR flash

Enable Renesas at25ql128a flash connected to QSPI0. Also disable
the node from rzfive-smarc-som as it is untested.

Tested the flash by flashing bootloaders:
flash_erase /dev/mtd0  0 0
flash_erase /dev/mtd1  0 0
mtd_debug write /dev/mtd0 0 ${BL2_FILE_SIZE} ${BL2_IMAGE}
mtd_debug write /dev/mtd1 512 ${FIP_FILE_SIZE} ${FIP_IMAGE}

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20241004173235.74307-2-biju.das.jz@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>