gralloc: update lock and lockYCbCr

IMapper 4.0 does support lockYCbCr functionality through lock and
BufferMetadata getters. However, we will wait to add the support in
one central gralloc library. For now just stub out the call so
there aren't any compiler errors.

Bug: 141631415
Test: Compiles

Change-Id: I9d2f70c87412f8ac2114db85eb6dc01539876e2b