selftests: connector: Add .gitignore and poupulate it with test

Add gitignore and poupulate it with test name - proc_filter

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/e3d04cc34e9af07909dc882b50fb1b6f1ce7705b.1690564372.git.skhan@linuxfoundation.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>