drm/vmwgfx: Make check_modeset() use the new atomic iterator macros.

drm/vmwgfx: Make check_modeset() use the new atomic iterator macros.

I don't think the checking of resources in this function is very
atomic-like, but it should definitely not use a macro that's about
to be removed.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Sinclair Yeh <syeh@vmware.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170712081344.25495-6-maarten.lankhorst@linux.intel.com
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[mlankhorst: Make function static (danvet)]