remove mmap-go so we can try to add it again as a submodule
remove mmap-go so we can try to add it again as a submodule

hugelgupf/u-root,u-root/u-root,rminnich/u-root,hugelgupf/u-root,hugelgupf/u-root,rminnich/u-root,GanShun/u-root,GanShun/u-root,rminnich/u-root,u-root/u-root,GanShun/u-root,hugelgupf/u-root,rminnich/u-root,u-root/u-root