Fix format string generation in pkg_printf.
Fix format string generation in pkg_printf.

As buf is passed as char * it is useless to apply sizeof operator
to it.

skoef/pkg,khorben/pkg,Open343/pkg,khorben/pkg,Open343/pkg,junovitch/pkg,en90/pkg,junovitch/pkg,khorben/pkg,skoef/pkg,en90/pkg