format warning on NetBSD 8 regarding unsigned int vs int

../../ntpd/ntp_control.c: In function 'ctl_getitem':
../../ntpd/ntp_control.c:2628:8: warning: format '%u' expects argument of type 'unsigned int', but argument 4 has t
ype 'int' [-Wformat=]
        "Possible 'ntpdx' exploit from %s#%u (possibly spoofed)",
        ^

/cc: @hal.murray