usb: musb: Fix trying to free already-free IRQ 4

When unloading omap2430, we can get the following splat:

WARNING: CPU: 1 PID: 295 at kernel/irq/manage.c:1478 __free_irq+0xa8/0x2c8
Trying to free already-free IRQ 4
...
[<c01a8b78>] (free_irq) from [<bf0aea84>]
(musbhs_dma_controller_destroy+0x28/0xb0 [musb_hdrc])
[<bf0aea84>] (musbhs_dma_controller_destroy [musb_hdrc]) from
[<bf09f88c>] (musb_remove+0xf0/0x12c [musb_hdrc])
[<bf09f88c>] (musb_remove [musb_hdrc]) from [<c056a384>]
(platform_drv_remove+0x24/0x3c)
...

This is because the irq number in use is 260 nowadays, and the dma
controller is using u8 instead of int.

Fixes: 6995eb68 ("USB: musb: enable low level DMA operation for Blackfin")
Signed-off-by: Tony Lindgren <tony@atomide.com>
[b-liu@ti.com: added Fixes tag]
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/musb/musbhsdma.h

@@ -157,5 +157,5 @@ struct musb_dma_controller {
 	void __iomem			*base;
 	u8				channel_count;
 	u8				used_channels;
-	u8				irq;
+	int				irq;
 };