speed is non-existent in PORT_TABLE of State-DB, but it is being set to N/A

[jaganbal-a]

With the PR: sonic-net/sonic-platform-daemons#254, it is found that speed field is being set to N/A in the STATE-DB.
If intended to update the 'speed' field in STATE-DB then the correct value should be updated.
If it is not supposed to be present, then resolve the code which is updating the speed field to STATE-DB port table.

PORT_TABLE object for Ethernet26
{'state': 'ok', 'netdev_oper_status': 'down', 'admin_status': 'down', 'mtu': '9100', 'supported_speeds': '', 'host_tx_ready': 'false', 'speed': 'N/A', 'index': '-1'}