[products] Fix router build deps

Resolves missing dependencies needed to build the router target:

  ERROR Unresolved dependencies.
  //:additional_base_packages(//build/toolchain/fuchsia:x64)
    needs //garnet/packages/prod:boringssl_tool(//build/toolchain/fuchsia:x64)
  //:additional_base_packages(//build/toolchain/fuchsia:x64)
    needs //garnet/packages/prod:dhcpd(//build/toolchain/fuchsia:x64)

Test: `fx set router.toulouse && fx build` works again:
Generating compile_commands took 459ms
Done. Made 23062 targets from 2038 files in 9725ms
...

Change-Id: Iab010faf19e4809ee736b31e8dac73d3ac5d556e