uio: Cleanup irq handling.

Change the value of UIO_IRQ_NONE -2 to 0.  0 is well defined in the rest
of the kernel as the value to indicate an irq has not been assigned.

Update the calls to request_irq and free_irq to only ignore UIO_IRQ_NONE
and UIO_IRQ_CUSTOM allowing the rest of the kernel's possible irq
numbers to be used.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Hans J. Koch <hjk@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 5dcc9ff..d6188e5 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -108,7 +108,7 @@
 
 /* defines for uio_info->irq */
 #define UIO_IRQ_CUSTOM	-1
-#define UIO_IRQ_NONE	-2
+#define UIO_IRQ_NONE	0
 
 /* defines for uio_mem->memtype */
 #define UIO_MEM_NONE	0