adv7511: Add poweron delay to allow for EDID probing to work

For some reason on HiKey960/970 the edid probing doesn't work
properly unless we delay a bit at poweron.

Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>