docs/freebsd: install golangci-lint on FreeBSD
docs/freebsd: install golangci-lint on FreeBSD

This is required for gmake presubmit.

google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller