selftests: add missing .gitignore file or entry

Only IPC selftest is missing the .gitignore file, so add it.
Also step_after_suspend_test is missing in breakpoints selftest
.gitignore file

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>