misc: Reserve minor for VFIO

VFIO currently allocates it's own dynamic chardev range, reserving the
first minor for the control part of the interface (/dev/vfio/vfio) and
the remainder for VFIO groups (/dev/vfio/$GROUP).  This works, but it
doesn't support auto loading.  For instance when libvirt checks for
VFIO support it looks for /dev/vfio/vfio, which currently doesn't
exist unless the vfio module is loaded.  By converting the control
device to a misc driver and reserving a static minor, we can enable
auto loading.

Reserving the minor is a prerequist to that conversion.  Minor 196
is unused by anything currently in the kernel.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h
index f7eaf2d..3737f72 100644
--- a/include/linux/miscdevice.h
+++ b/include/linux/miscdevice.h
@@ -30,6 +30,7 @@
 #define STORE_QUEUE_MINOR	155
 #define I2O_MINOR		166
 #define MICROCODE_MINOR		184
+#define VFIO_MINOR		196
 #define TUN_MINOR		200
 #define CUSE_MINOR		203
 #define MWAVE_MINOR		219	/* ACP/Mwave Modem */