i40iw: Redefine i40iw_mmiowb() to do nothing

mmiowb() is now implicit in spin_unlock(), so there's no reason to call
it from driver code. Redefine i40iw_mmiowb() to do nothing instead.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

drivers/infiniband/hw/i40iw/i40iw_osdep.h

@@ -211,7 +211,7 @@ enum i40iw_status_code i40iw_hw_manage_vf_pble_bp(struct i40iw_device *iwdev,
 struct i40iw_sc_vsi;
 void i40iw_hw_stats_start_timer(struct i40iw_sc_vsi *vsi);
 void i40iw_hw_stats_stop_timer(struct i40iw_sc_vsi *vsi);
-#define i40iw_mmiowb() mmiowb()
+#define i40iw_mmiowb() do { } while (0)
 void i40iw_wr32(struct i40iw_hw *hw, u32 reg, u32 value);
 u32  i40iw_rd32(struct i40iw_hw *hw, u32 reg);
 #endif				/* _I40IW_OSDEP_H_ */