drm/amd/display: resolve correct MALL size for dcn401

[WHY]
Code for dcn401 to calculate available MALL size for display was shared
with dcn32 and did not provide the correct result for all ASICs.

[HOW]
Add dcn401 specific function to properly calculate the available MALL
for display.

Reviewed-by: Chris Park <chris.park@amd.com>
Signed-off-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>