libbinder_ndk: Add default constructor for SpAIBinder

This allows for default construction of SpAIBinder and AIDL structured parcelables.

Bug: None
Test: atest CtsNdkBinderTestCases binderVendorDoubleLoadTest libbinder_ndk_unit_test
Change-Id: Ia2c6371e828f92cc0a42b3c57fcec3d11f3fedc6
1 file changed