octeontx2-bphy-netdev: Fix ptp pending skb list processing

commit 97380ebe900400eec778c046f8f80510919d3491 from
git@git.assembla.com:cavium/WindRiver.linux.git

Fix ptp skb pending list processing logic to get the first
list entry and queue the packet for processing.

Change-Id: Ib0565a2f38a338683e9539c7252d6ad2a0712fb5
Signed-off-by: Naveen Mamindlapalli <naveenm@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/38227


Tested-by: sa_ip-sw-jenkins <sa_ip-sw-jenkins@marvell.com>
Reviewed-by: Sunil Kovvuri Goutham <Sunil.Goutham@cavium.com>
Signed-off-by: Ruiqiang Hao <Ruiqiang.Hao@windriver.com>