drm/amd/display: Use DCC meta pitch for MALL allocation requirements

[Description]
Calculations for determining DCC meta size should be pitch*height*bpp/256.

Reviewed-by: Alvin Lee <Alvin.Lee2@amd.com>
Acked-by: Jasdeep Dhillon <jdhillon@amd.com>
Signed-off-by: Dillon Varone <Dillon.Varone@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>