drm/amd/display: fix a regression in blank pixel data caused by coding mistake

drm/amd/display: fix a regression in blank pixel data caused by coding mistake

[why]
There was unfortunately a coding mistake. It gets caught with an ultrawide monitor
that requires ODM 4:1 combine. We are blanking or unblanking pixel data we
are supposed to enumerate through all ODM pipes and program DPG for each
of those pipes. However the coding mistake causes us to program only the
first and last ODM pipes.

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Martin Leung <martin.leung@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>