This doesn't yet cover input, but the driver does get the display
working when the firmware is disabled from talking to our I2C lines.
Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20170927193654.12609-3-eric@anholt.net