drm/msm/dp: unplug interrupt missed after irq_hpd handler

There is HPD unplug interrupts missed at scenario of an irq_hpd
followed by unplug interrupts with around 10 ms in between.
Since both AUX_SW_RESET and DP_SW_RESET clear pending HPD interrupts,
irq_hpd handler should not issues either aux or sw reset to avoid
following unplug interrupt be cleared accidentally. This patch
also postpone handling of irq_hpd until connected state if it
happened at connection pending state.

Changes in V2:
-- add postpone handling of irq_hpd until connected state
-- check DP_TRAINING_1 instead of DP_TRAINING_NONE

Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>