The BL2 image for mt7987_rfb-emmc should be emmc, not sdmmc.
Fixes: 6d35eda ("uboot-mediatek: add builds for the MediaTek MT7987 reference board")
Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Link: https://github.com/openwrt/openwrt/pull/23490
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>