OvmfPkg: increase max debug message length to 512
    
    Increase the maximum line length for debug messages.
    While log messages should be short, they can still
    get quite long, for example when printing device paths
    or config strings in HII routing.
    512 chars is an empirically good value.
    
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>
    Signed-off-by: Oliver Steffen <osteffen@redhat.com>
    Acked-by: Gerd Hoffmann <kraxel@redhat.com>