CHROMIUM: config: Enable it6505 config.

The change is generated from the following commands:

cat <<EOF | tee -a \
   chromeos/config/arm64/chromiumos-arm64.flavour.config \
   chromeos/config/arm64/chromiumos-mediatek.flavour.config

CONFIG_DRM_ITE_IT6505=y

EOF

./chromeos/scripts/kernelconfig olddefconfig

BUG=b:126007406
TEST=build succeed.

Change-Id: Iea98ebd80cfac6df772d4f79549a2f41ebc779e4
Signed-off-by: Pi-Hsun Shih <pihsun@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1561152
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
Commit-Queue: Nicolas Boichat <drinkcat@chromium.org>