drm/amd/display: Fix FCLK deviation and tool compile issues

drm/amd/display: Fix FCLK deviation and tool compile issues

[Why]
Recent backports from open source do not have header inclusion pattern
that is consistent with inclusion style in the rest of the file. This
breaks the internal tool builds as well. A recent commit erronously
modified the original DML formula for calculating
ActiveClockChangeLatencyHidingY. This resulted in a FCLK deviation
from the golden values.

[How]
Change the way in which display_mode_vba.h is included so that it is
consistent with the inclusion style in rest of the file which also fixes
the tool build. Restore the DML formula to its original state to fix the
FCLK deviation.

Reviewed-by: Aurabindo Pillai <Aurabindo.Pillai@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Alan Liu <HaoPing.Liu@amd.com>
Signed-off-by: Chaitanya Dhere <chaitanya.dhere@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>