docs: drivers: fix some warnings at base/platform.c when building docs

Currrently, two warnings are generated when building docs:

	./drivers/base/platform.c:136: WARNING: Unexpected indentation.
	./drivers/base/platform.c:214: WARNING: Unexpected indentation.

As examples are code blocks, they should use "::" markup. However,

	Example::

Is currently interpreted as a new section.

While we could fix kernel-doc to accept such new syntax, it is
easier to just replace it with:

	For Example::

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/564273815a76136fb5e453969b1012a786d99e28.1586881715.git.mchehab+huawei@kernel.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>