mediatek/mt8183: Remove the stub flash driver that planned to use eMMC

The stub flash driver is a temporary hack that planned to adapt eMMC to
SPI flash. Remove the hack since SPI flash is what we really expect.

BUG=b:80501386
BRANCH=none
TEST=Boots fine on Kukui

Change-Id: If29869461fc8c2efe26bb8c901737ee85935d27f
Signed-off-by: Tristan Shieh <tristan.shieh@mediatek.com>
Reviewed-on: https://review.coreboot.org/27114
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
3 files changed