drm/amd/display: avoid variable reinitialization

The member variable enable_hpo_pg_support is already initialized
and hence the reinitialization instruction can be removed. Issue
identified using the doubleinit.cocci Coccinelle semantic patch script.

Signed-off-by: Bragatheswaran Manickavel <bragathemanick0908@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>