drm/nv4c/mc: disable msi

commit 4761703b upstream.

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: fa8c9ac7 ("drm/nv4c/mc: nv4x igp's have a different msi rearm register")
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/gpu/drm/nouveau/core/subdev/mc/nv4c.c

@@ -24,13 +24,6 @@
 
 #include "nv04.h"
 
-static void
-nv4c_mc_msi_rearm(struct nouveau_mc *pmc)
-{
-	struct nv04_mc_priv *priv = (void *)pmc;
-	nv_wr08(priv, 0x088050, 0xff);
-}
-
 struct nouveau_oclass *
 nv4c_mc_oclass = &(struct nouveau_mc_oclass) {
 	.base.handle = NV_SUBDEV(MC, 0x4c),
@@ -41,5 +34,4 @@ nv4c_mc_oclass = &(struct nouveau_mc_oclass) {
 		.fini = _nouveau_mc_fini,
 	},
 	.intr = nv04_mc_intr,
-	.msi_rearm = nv4c_mc_msi_rearm,
 }.base;