drm/amd/display: extending AUX SW Timeout

[Why]
AUX takes longer to reply when using active DP-DVI dongle on some asics
resulting in up to 2000+ us edid read (timeout).

[How]
1. Adjust AUX poll to match spec
2. Extend the SW timeout. This does not affect normal
operation since we exit the loop as soon as AUX acks.

Signed-off-by: Martin Leung <martin.leung@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Joshua Aberback <Joshua.Aberback@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>