myri10ge: make msi configurable at runtime through sysfs

Now that IRQ are requested is called on open() and freed on close(),
we can safely switch from/to MSI without unloading the module.

We are guaranteed to correctly free IRQ even if the sysfs file got
written in the meantime since the MSI initialization is stored in
mgp->msi_enabled.
Signed-off-by: Brice Goglin <brice@myri.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/myri10ge/myri10ge.c

@@ -228,7 +228,7 @@ module_param(myri10ge_small_bytes, int, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(myri10ge_small_bytes, "Threshold of small packets\n");
 
 static int myri10ge_msi = 1;	/* enable msi by default */
-module_param(myri10ge_msi, int, S_IRUGO);
+module_param(myri10ge_msi, int, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(myri10ge_msi, "Enable Message Signalled Interrupts\n");
 
 static int myri10ge_intr_coal_delay = 25;