drm/nv4c/mc: disable msi

Several users have, over time, reported issues with MSI on these IGPs.
They're old, rarely available, and MSI doesn't provide such huge
advantages on them. Just disable.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=87361
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=74492
Fixes: fa8c9ac72fe ("drm/nv4c/mc: nv4x igp's have a different msi rearm register")
Cc: stable@vger.kernel.org
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>