smc: fix out of bound access in smc_nl_get_sys_info()

smc_clc_get_hostname() sets the host pointer to a buffer
which is not NULL-terminated (see smc_clc_init()).

Reported-by:  <syzbot+f4708c391121cfc58396@syzkaller.appspotmail.com>
Fixes: 099b990b ("net/smc: Add support for obtaining system information")
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>