drm/amd/display: Wait until OTG enable state is cleared

[Why]
Customer reported an issue that OS starts and stops device multiple times
during driver installation. Frequently disabling and enabling OTG may
prevent OTG from being safely disabled and cause incorrect configuration
upon the next enablement.

[How]
Add a wait until OTG_CURRENT_MASTER_EN_STATE is cleared as a short term
solution.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: TungYu Lu <tungyu.lu@amd.com>
Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>