Documentation: fix typos found in process, dev-tools, and doc-guide subdirectories

Fix four typos in kcov.rst, sphinx.rst, clang-format.rst, and embargoed-hardware-issues.rst

Signed-off-by: Andrew Klychkov <andrew.a.klychkov@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20201202075438.GA35516@spblnx124.lan


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