Revert "wrc.h: define printf as pp_printf"

This reverts commit 0bcbe429.

Now that we are able to check for bogus printf calls, don't define the
name any more (ptp-noposix defines it anyways, but let's not do it
when building with ppsi, so the code explicitly calls pp_printf (or
mprintf, which will remain as an alias until we get rid of
ptp-noposix).
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>