docs: improve setup.md
docs: improve setup.md

This patch improve the following in setup.md:

  - Do not set btrfs-progs-devel package as required
    package for installation.

  - For Fedora/CentOS steps: add make as requirement.

  - Add to RHEL8 steps: pkgconf-pkg-config package
    (replacement for pkgconfig).

  - Add a note about btrfs-progs-devel and pkgconfig
    replacement.

Signed-off-by: Douglas Schilling Landgraf <cb5f9630225b7afa1e13760d30868c8ce876fc60@redhat.com>

mikebrow/cri-o,mikebrow/cri-o,mikebrow/cri-o,kubernetes-incubator/cri-o,nalind/cri-o,kubernetes-incubator/cri-o,kubernetes-incubator/ocid,mikebrow/cri-o,nalind/cri-o,kubernetes-incubator/cri-o,nalind/cri-o,kubernetes-incubator/ocid,kubernetes-incubator/ocid,kubernetes-incubator/cri-o