drm/amd/display: Fix stack size issue on DML2

This commit is the last part of the fix that reduces the stack size in
the DML2 code.

Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Roman Li <roman.li@amd.com>
Cc: Chaitanya Dhere <chaitanya.dhere@amd.com>
Fixes: 7966f319 ("drm/amd/display: Introduce DML2")
Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>