Documentation: kunit: Update Kconfig parts for KUNIT's module support

If 'CONFIG_KUNIT=m', letting kunit tests that do not support loadable
module build depends on 'KUNIT' instead of 'KUNIT=y' result in compile
errors.  This commit updates the document for this.

Fixes: 9fe124bf ("kunit: allow kunit to be loaded as a module")
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: David Gow <davidgow@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Documentation/dev-tools/kunit/start.rst

@@ -197,7 +197,7 @@ Now add the following to ``drivers/misc/Kconfig``:
 
 	config MISC_EXAMPLE_TEST
 		bool "Test for my example"
-		depends on MISC_EXAMPLE && KUNIT
+		depends on MISC_EXAMPLE && KUNIT=y
 
 and the following to ``drivers/misc/Makefile``:
 

Documentation/dev-tools/kunit/usage.rst

@@ -561,6 +561,11 @@ Once the kernel is built and installed, a simple
 
 ...will run the tests.
 
+.. note::
+   Note that you should make sure your test depends on ``KUNIT=y`` in Kconfig
+   if the test does not support module build.  Otherwise, it will trigger
+   compile errors if ``CONFIG_KUNIT`` is ``m``.
+
 Writing new tests for other architectures
 -----------------------------------------