wimax: fix gcc warnings in sh4 when calling BUG()

SH4's BUG() seems to confuse the compiler as it is considered to
return; thus, some functions would trigger usage of uninitialized
variables or non-void functions returning void.

Work around by initializing/returning.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
diff --git a/drivers/net/wimax/i2400m/usb.c b/drivers/net/wimax/i2400m/usb.c
index ebc05da..cfdaf69 100644
--- a/drivers/net/wimax/i2400m/usb.c
+++ b/drivers/net/wimax/i2400m/usb.c
@@ -254,8 +254,10 @@
 			dev_err(dev, "USB reset failed (%d), giving up!\n",
 				result);
 		}
-	} else
+	} else {
+		result = -EINVAL;	/* shut gcc up in certain arches */
 		BUG();
+	}
 	if (result < 0
 	    && result != -EINVAL	/* device is gone */
 	    && rt != I2400M_RT_BUS) {