Change GraphicBuffer fields from uint to int

This changes fields which are tracking GraphicBuffer width and height
to use int instead of uint32_t, which is in keeping with a recent
change to GraphicBuffer itself and avoids a warning (error since this
build uses -Werror).

Change-Id: I66c5c3e3d321d4ef5ea2c40c86ac068111c18662
1 file changed