net: pch_gbe: remove unneeded variable retval in __pch_gbe_suspend

Fix the following coccicheck warning:

./drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe_main.c:2415:5-11: Unneeded variable: "retval". Return "0" on line 2435

Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Link: https://lore.kernel.org/r/1604837580-12419-1-git-send-email-kaixuxia@tencent.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>