docs: dev-tools: testing-overview.rst: avoid using ReST :doc:`foo` markup

The :doc:`foo` tag is auto-generated via automarkup.py.
So, use the filename at the sources, instead of :doc:`foo`.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/6bbecd4170ee08f36f8060b0719a46c64a21aefc.1623824363.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/dev-tools/testing-overview.rst

@@ -71,15 +71,15 @@ can be used to verify that a test is executing particular functions or lines
 of code. This is useful for determining how much of the kernel is being tested,
 and for finding corner-cases which are not covered by the appropriate test.
 
-:doc:`gcov` is GCC's coverage testing tool, which can be used with the kernel
-to get global or per-module coverage. Unlike KCOV, it does not record per-task
-coverage. Coverage data can be read from debugfs, and interpreted using the
-usual gcov tooling.
+Documentation/dev-tools/gcov.rst is GCC's coverage testing tool, which can be
+used with the kernel to get global or per-module coverage. Unlike KCOV, it
+does not record per-task coverage. Coverage data can be read from debugfs,
+and interpreted using the usual gcov tooling.
 
-:doc:`kcov` is a feature which can be built in to the kernel to allow
-capturing coverage on a per-task level. It's therefore useful for fuzzing and
-other situations where information about code executed during, for example, a
-single syscall is useful.
+Documentation/dev-tools/kcov.rst is a feature which can be built in to the
+kernel to allow capturing coverage on a per-task level. It's therefore useful
+for fuzzing and other situations where information about code executed during,
+for example, a single syscall is useful.
 
 
 Dynamic Analysis Tools