tcpslice: fix do_install

replace to run "make install" with directly calling install command,
since "make install" asks "bin" user and group, and maybe fail when
system has not;

Signed-off-by: Roy Li <rongqing.li@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>