Revert "DocBook: Avoid building man pages repeatedly and inconsistently"

This reverts commit b44158b17099ed5c7c8f4bfb7029942adbfbc318.  This commit
introduced warnings and possibly inconsistent results into the doc build
process.  The goal is good but it will need to be achieved another way.

Reported-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --cc Documentation/DocBook/Makefile
Simple merge

diff --cc Documentation/DocBook/device-drivers.tmpl
Simple merge

diff --cc Documentation/DocBook/gadget.tmpl
Simple merge

diff --cc Documentation/DocBook/kernel-api.tmpl
Simple merge