ixgbe: add SFP+ LX module support

This patch adds LX support to 82599 devices. This is an alternate patch to
the one suggested by Stefan Behte <s.behte@babiel.com>

In addition this patch includes some cleanups such as:
- removed parenthesis around "x == y ||" lines inside an if statement for
consistency.
- grouped the sx/lx sfp types along with srlr in ixgbe_get_settings() since
they all have the same supported, advertised and port values.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Reported-by: Stefan Behte <s.behte@babiel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>