networking: e1000.rst: Get rid of Sphinx warnings

Documentation/networking/e1000.rst:83: ERROR: Unexpected indentation.
    Documentation/networking/e1000.rst:84: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/networking/e1000.rst:173: WARNING: Definition list ends without a blank line; unexpected unindent.
    Documentation/networking/e1000.rst:236: WARNING: Definition list ends without a blank line; unexpected unindent.

While here, fix highlights and mark a table as such.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>