net: pcs: lynx: use a common naming scheme for all lynx_pcs variables

pcs-lynx.c used lynx_pcs and lynx as a variable name within the same file.
This standardizes all internal variables to just "lynx"

Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
Signed-off-by: David S. Miller <davem@davemloft.net>