MLK-20481: hdp: change hdmi keep-alive check mechanism

MLK-20481: hdp: change hdmi keep-alive check mechanism

The current keep-alive check mechanism uses a static variable
that is initialized to 0. When the function is first called, it may
happen to catch the 8-bit keep-alive counter right when it
overflows, hence returning BUSY.

This patch will keep checking the counter for 10us, every 1us,
but it will immediately return if the keep-alive counter changed.

Signed-off-by: Laurentiu Palcu<laurentiu.palcu@nxp.com>
Signed-off-by: Sandor Yu <Sandor.yu@nxp.com>