build: install BCC PMDA config files below /etc not /usr
build: install BCC PMDA config files below /etc not /usr

Noticed by Marko recently (thanks!) - /usr is indeed not
the intended home for these files.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp