drm/amd/display: Add support for custom recout_width in SPL

[WHY]
Add support for custom recout_width for mpc combine in SPL

[HOW]
1. Rename mpc_combine_h and mpc_combine_v
2. Add flag use_recout_width_aligned to use custom recout_width
3. Create union to use either mpc_num_h_slices or mpc_recout_width_align

Reviewed-by: Navid Assadian <navid.assadian@amd.com>
Signed-off-by: Samson Tam <Samson.Tam@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>