Revert "ifconfig: Display the IFCAP_NV capability without netlink"

The display of IFCAP_NV is handled by SIOCGIFCAPNV ioctl. The kernel
composes a nvlist of capabilities and the userland unpack them and
display. So this "NV" in IFCAPBITS is meaningless but rather misleading.

This reverts commit 0c1684dd456e3df306b359b04e61f9f2048d9ff2.