NTB: Fix documentation for ntb_link_is_up

There was a copy and paste error in the documentation for
ntb_link_is_up.  The long description was mistakenly copied from
ntb_link_set_trans.

This adds the appropriate long description for ntb_link_is_up.

Reported-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Allen Hubbe <Allen.Hubbe@emc.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

include/linux/ntb.h

@@ -522,10 +522,9 @@ static inline int ntb_mw_clear_trans(struct ntb_dev *ntb, int idx)
  * @speed:	OUT - The link speed expressed as PCIe generation number.
  * @width:	OUT - The link width expressed as the number of PCIe lanes.
  *
- * Set the translation of a memory window.  The peer may access local memory
- * through the window starting at the address, up to the size.  The address
- * must be aligned to the alignment specified by ntb_mw_get_range().  The size
- * must be aligned to the size alignment specified by ntb_mw_get_range().
+ * Get the current state of the ntb link.  It is recommended to query the link
+ * state once after every link event.  It is safe to query the link state in
+ * the context of the link event callback.
  *
  * Return: One if the link is up, zero if the link is down, otherwise a
  *		negative value indicating the error number.