drm/amd/display: Renoir chroma viewport WA change formula

[why]
we want to increase the pte row plus 1 line if chroma viewport
height is integer multiple of the pte row height

[how]
instead of ceiling viewport height, we floor it. this allows
us to accommodate both cases: those where the chroma viewport
height is integer multiple of the pte row height and those where
it is not

Signed-off-by: Joseph Gravenor <joseph.gravenor@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>