uml: vector: Remove unused definitions VECTOR_{WRITE,HEADERS}

Remove definitions of VECTOR_WRITE and VECTOR_HEADERS since no longer used.

Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>