selftests: kvm: add generated file to the .gitignore

Add hyperv_svm_test to the .gitignore file.

Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>