Remove gfs2/include/linux_endian.h
    
    Archaeology time. This header is a remnant of the integrated cluster.git
    days and only tunegfs2 ever used it. The useful byte swapping functions
    in it were added to libgfs2.h a long time ago so it is unneeded.
    
    Signed-off-by: Andrew Price <anprice@redhat.com>