Seems ntpdate also requires this lib:
```
Package ntpdate is missing dependencies for the following libraries:
libcap.so.2
make[2]: *** [/store/buildbot/slave/ar71xx/build/bin/ar71xx/packages/packages/ntpdate_4.2.8p4-1_ar71xx.ipk] Error 1
make[2]: Leaving directory `/store/buildbot/slave/ar71xx/build/feeds/packages/net/ntpd'
```

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>