x86/UV: Fix conditional in gru_exit()

Fix supported system conditional in gru_exit(), in preparation for UV3.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Link: http://lkml.kernel.org/r/20140331152320.GA31495@sgi.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>