drm/amd/display: Reduce stack size

Linux kernel enabled more compilation restrictions related to the stack
size, which caused compilation failures in our code. This commit reduces
the allocation size by allocating the required memory dynamically.

Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>