drm/amdgpu/display: use kvzalloc again in dc_create_state

It looks this was accidently lost in a follow up patch.
dc context is large and we don't need contiguous pages.

Fixes: e4863f11 ("drm/amd/display: Multi display cause system lag on mode change")
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Aric Cyr <aric.cyr@amd.com>
Cc: Alex Xu <alex_y_xu@yahoo.ca>
Reported-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca>
Tested-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca>
Cc: stable@vger.kernel.org