igc: remove unnecessary PHY ID checks

I225 devices have only one PHY vendor. There is unnecessary to check
_I_PHY_ID during the link establishment and auto-negotiation process,
the checking also caused devices like i225-IT failed. This patch is to
remove the mentioned unnecessary checking.

Cc: stable@dpdk.org

Signed-off-by: Mah Yock Gen <yock.gen.mah@intel.com>
Signed-off-by: Taripin Samuel <samuel.taripin@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>

Approved by: grehan
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D36923