i40e: PTP - avoid aggregate return warnings

Aggregate return warnings are when struct types are returned
and must be copied to the lvalue with a struct copy by the compiler.

This fixes warnings of type aggregate-return from gcc with W=2.

Change-Id: I896b1bf514544bf0faeb458869d79914b9f1b168
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_ptp.c

@@ -158,9 +158,10 @@ static int i40e_ptp_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
 static int i40e_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
 {
 	struct i40e_pf *pf = container_of(ptp, struct i40e_pf, ptp_caps);
-	struct timespec64 now, then = ns_to_timespec64(delta);
+	struct timespec64 now, then;
 	unsigned long flags;
 
+	then = ns_to_timespec64(delta);
 	spin_lock_irqsave(&pf->tmreg_lock, flags);
 
 	i40e_ptp_read(pf, &now);