[why]
Currently link bandwidth is calculated in two places, using the same
formula. They should be unified into calling one function.

[how]
Replace all implementations of link bandwidth calculation with a call
to a function.
Signed-off-by: NNikola Cornij <nikola.cornij@amd.com>
Reviewed-by: NNikola Cornij <Nikola.Cornij@amd.com>
Acked-by: NLeo Li <sunpeng.li@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>