i40e: Fix ethtool coalesce settings

This patch fixes the i40e_set_coalesce function to allow 0 as a disable
value.  Also, added message to user about invalid value and provides valid
range.

Change-ID: I6c9ff11a9861f2045bd543745a3d132999ffbbd8
Signed-off-by: Carolyn Wyborny <carolyn.wyborny@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index b4278a2..71efc68 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -2768,6 +2768,22 @@
 }
 
 /**
+ * i40e_irq_dynamic_disable - Disable default interrupt generation settings
+ * @vsi: pointer to a vsi
+ * @vector: enable a particular Hw Interrupt vector
+ **/
+void i40e_irq_dynamic_disable(struct i40e_vsi *vsi, int vector)
+{
+	struct i40e_pf *pf = vsi->back;
+	struct i40e_hw *hw = &pf->hw;
+	u32 val;
+
+	val = I40E_ITR_NONE << I40E_PFINT_DYN_CTLN_ITR_INDX_SHIFT;
+	wr32(hw, I40E_PFINT_DYN_CTLN(vector - 1), val);
+	i40e_flush(hw);
+}
+
+/**
  * i40e_msix_clean_rings - MSIX mode Interrupt Handler
  * @irq: interrupt number
  * @data: pointer to a q_vector