libpcap: Fix dependency definitions for libpcap

[markj]

Summary

Commit 35dd53a9e132 ("librdmacm/libibverbs: Statically bound libbnxtre.so.1 to rping")
causes a build failure, since src.libnames.mk declares a depencency on
libbnxtre.so, but the libpcap Makefile and prebuild lib dependencies
were not updated accordingly.

Assuming that the original change was intentional, fix the declarations.

[sumit.saxena_broadcom.com]

Thanks for taking care of this. We have also identified similar changes and with this "make buildworld" compiles..