networking: e100.rst: Get rid of Sphinx warnings

Documentation/networking/e100.rst:57: WARNING: Literal block expected; none found.
    Documentation/networking/e100.rst:68: WARNING: Literal block expected; none found.
    Documentation/networking/e100.rst:75: WARNING: Literal block expected; none found.
    Documentation/networking/e100.rst:84: WARNING: Literal block expected; none found.
    Documentation/networking/e100.rst:93: WARNING: Inline emphasis start-string without end-string.

While here, fix some highlights.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>