docs: don't use nested tables

Nested tables aren't supported for pdf output on Sphinx 1.7.9:

	admin-guide/laptops/sonypi:: nested tables are not yet implemented.
	admin-guide/laptops/toshiba_haps:: nested tables are not yet implemented.
	driver-api/nvdimm/btt:: nested tables are not yet implemented.
	s390/debugging390:: nested tables are not yet implemented.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com> # laptops