librumpxen_xendev: Do not test uio->uio_offset in xenbus_dev_write

This field is undefined on entry to f_write functions.

(The copying of the file offset to and from this field is done by
vn_read and vn_write, only for vnode entries, which this isn't.)

Signed-off-by: Ian Jackson <[email protected]>

Author: ijackson-citrix

platform/xen/librumpxen_xendev/busdev.c

@@ -116,9 +116,6 @@ xenbus_dev_write(struct file *fp, off_t *offset, struct uio *uio,
 
 	DPRINTF(("/dev/xen/xenbus[%p,dd=%p]: write...\n",dc,dd));
 
-	if (uio->uio_offset < 0)
-		return EINVAL;
-
 	mutex_enter(&dd->lock);
 
 	for (;;) { /* keep reading more until we're done */