iio: ABI: sysfs-bus-iio: avoid a warning when doc is built

The description of those vars produce this warning:
  Documentation/ABI/testing/sysfs-bus-iio:799: WARNING: Inline emphasis start-string without end-string.

Due to an asterisk, which is the markup for emphasis. One possible
fix would be to use ``*_timeout`` to avoid it, but looking at
the descriptions of other fields in this file, a common pattern
is to refer to "these" when talking about the API calls that
are described.

So, change the text in order to preserve the meaning while
avoiding the need of using an asterisk there.

Reported-by: Jonathan Corbet <corbet@lwn.net>
Reported-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/dbf0d94f85217f103d77dc8389c8db272f5702d2.1621944866.git.mchehab+huawei@kernel.org


[jc fixed specifiy->specify]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>