libpam: remove autoreconf call from configure macro

Hello,

I am not so experienced with autoreconf, but the following patch
fixes the package breakage which can be seen in buildbot logs.
Autoreconf call is also specified in PKG_FIXUP variable.

Jiri

git-svn-id: svn://svn.openwrt.org/openwrt/packages@38525 3c298f89-4303-0410-b956-a3cf2f4a3e73