drm/amd/display: Add option to configure mapping policy for edp0 on dp1

drm/amd/display: Add option to configure mapping policy for edp0 on dp1

[Why]
We want flexibility to choose how pwrseq instance is mapped to eDP panel

[How]
Add configuration option to choose the pwrseq mapping policy.
When enabled, allow fixed mapping between DIG inst to pwrseq inst.

Reviewed-by: Anthony Koo <anthony.koo@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Lewis Huang <lewis.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>