drm/radeon/kms: Add MSI quirk for Dell RS690

Some Dell laptops only seem to work with MSIs.  This
looks like a platform/bios bug.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=37679



Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>