sfc: Add a function pointer to abstract write of host time into NIC shared memory

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/ethernet/sfc/siena.c b/drivers/net/ethernet/sfc/siena.c
index a51d90c..3c0a544 100644
--- a/drivers/net/ethernet/sfc/siena.c
+++ b/drivers/net/ethernet/sfc/siena.c
@@ -855,6 +855,19 @@
 
 /**************************************************************************
  *
+ * PTP
+ *
+ **************************************************************************
+ */
+
+static void siena_ptp_write_host_time(struct efx_nic *efx, u32 host_time)
+{
+	_efx_writed(efx, cpu_to_le32(host_time),
+		    FR_CZ_MC_TREG_SMEM + MC_SMEM_P0_PTP_TIME_OFST);
+}
+
+/**************************************************************************
+ *
  * Revision-dependent attributes used by efx.c and nic.c
  *
  **************************************************************************
@@ -943,6 +956,7 @@
 	.mtd_write = efx_mcdi_mtd_write,
 	.mtd_sync = efx_mcdi_mtd_sync,
 #endif
+	.ptp_write_host_time = siena_ptp_write_host_time,
 
 	.revision = EFX_REV_SIENA_A0,
 	.txd_ptr_tbl_base = FR_BZ_TX_DESC_PTR_TBL,