drm/amd/display: move calcs folder into DML

The calcs folder has FPU code on it, which should be isolated inside the
DML folder as per https://patchwork.freedesktop.org/series/93042/.

This commit aims single-handedly to correct the location of such FPU
code and does not refactor any functions.

Changes since v2:
- Corrected problems to compile when DCN was disabled.

Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Isabella Basso <isabbasso@riseup.net>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>