.gitignore: Unignore .kunitconfig

There are almost dozen of .kunitconfig files that are ignored but
tracked. Unignore them.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

.gitignore

@@ -102,6 +102,7 @@ modules.order
 !.get_maintainer.ignore
 !.gitattributes
 !.gitignore
+!.kunitconfig
 !.mailmap
 !.rustfmt.toml