Revert "drm/amd/display: edp do not add non-edid timings"

This change causes regression when eDP and external display in mirror
mode. When external display supports low resolution than eDP, use eDP
timing to driver external display may cause corruption on external
display.

This reverts commit e749dd10.

Cc: stable@vger.kernel.org
Link: drm/amd#2655


Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>