Fix speed parsing when speed if not fetched from APPL_DB

[keboliu]

Signed-off-by: Kebo Liu kebol@nvidia.com

What I did

In PR sonic-net#2110 introduced an enhancement to support display port speed with different unit when it is RJ45 ports, however, it only covered the case that the speed was fetched from APPL_DB.
Recently there is a change to fetch the speed from STATE_DB in some cases, the same logic also needs to be applied in this case.

How I did it

1. rename appl_db_port_speed_parse to a more generic name port_speed_parse
2. call port_speed_parse when speed is fetched from STATE_DB

How to verify it

UT and test it on platform support RJ45 ports

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)