drm/amd/display/dml2: use vzalloc rather than kzalloc

The structures are large and they do not require contiguous
memory so use vzalloc.

Fixes: 70839da6 ("drm/amd/display: Add new DCN401 sources")
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4126


Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>