ia64: fix panic during `modprobe -r xpc'

If you are on ia64 and you modprobe xpc then modprobe -r xpc, you
immediately get a panic.  xpc depends on xp which depends on gru for a
symbol.  That symbol is only used when we are running on UV hardware.

Currently, the GRU driver detects we are not on UV hardware and does no
initializing.  It does not do the same check when unloading.  As a result,
the gru driver attempts to tear down stuff that was not setup.

This is a simple two-line workaround to get us through this release.  Once
2.6.28 is opened, we need to rework the symbols that xp is depending on
from gru so the gru driver can properly fail to load when hardware is not
available.
Signed-off-by: NRobin Holt <holt@sgi.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/misc/sgi-gru/grufile.c

@@ -445,6 +445,9 @@ static void __exit gru_exit(void)
 	int order = get_order(sizeof(struct gru_state) *
 			      GRU_CHIPLETS_PER_BLADE);
 
+	if (!IS_UV())
+		return;
+
 	for (i = 0; i < GRU_CHIPLETS_PER_BLADE; i++)
 		free_irq(IRQ_GRU + i, NULL);