um: Implement um_free_irq()

Instead of using chip->release() we can achieve the same
using a simple wrapper for free_irq().
We have already um_request_irq(), so um_free_irq() is the perfect
counterpart.

Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index ca4c7eb..45e248c 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -8,6 +8,7 @@
 #include <linux/tty_flip.h>
 #include "chan.h"
 #include "os.h"
+#include "irq_kern.h"
 
 #ifdef CONFIG_NOCONFIG_CHAN
 static void *not_configged_init(char *str, int device,
@@ -213,9 +214,9 @@
 		chan = list_entry(ele, struct chan, free_list);
 
 		if (chan->input && chan->enabled)
-			free_irq(chan->line->driver->read_irq, chan);
+			um_free_irq(chan->line->driver->read_irq, chan);
 		if (chan->output && chan->enabled)
-			free_irq(chan->line->driver->write_irq, chan);
+			um_free_irq(chan->line->driver->write_irq, chan);
 		chan->enabled = 0;
 	}
 }
@@ -234,9 +235,9 @@
 	}
 	else {
 		if (chan->input && chan->enabled)
-			free_irq(chan->line->driver->read_irq, chan);
+			um_free_irq(chan->line->driver->read_irq, chan);
 		if (chan->output && chan->enabled)
-			free_irq(chan->line->driver->write_irq, chan);
+			um_free_irq(chan->line->driver->write_irq, chan);
 		chan->enabled = 0;
 	}
 	if (chan->ops->close != NULL)