drm/amd/display: fix image corruption with ODM 2:1 DSC 2 slice

[why]
When combining two or more pipes in DSC mode, there will always be more
than 1 slice per line.  In this case, as per DSC rules, the sink device
is expecting that the ICH is reset at the end of each slice line (i.e.
ICH_RESET_AT_END_OF_LINE must be configured based on the number of
slices at the output of ODM).  It is recommended that software set
ICH_RESET_AT_END_OF_LINE = 0xF for each DSC in the ODM combine.  However
the current code only set ICH_RESET_AT_END_OF_LINE = 0xF when number of
slice per DSC engine is greater than 1 instead of number of slice per
output after ODM combine.

[how]
Add is_odm in dsc config. Set ICH_RESET_AT_END_OF_LINE = 0xF if either
is_odm or number of slice per DSC engine is greater than 1.

Signed-off-by: Wenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: Nikola Cornij <Nikola.Cornij@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>