drm/amd/display: Update gpuvm_max_page_table_levels IP param

After some experimental tests, we noticed that we need to set
gpuvm_max_page_table_levels to '4' to meet the hardware requirements.

Signed-off-by: Eric Bernstein <eric.bernstein@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>