php: fix more iconv related build failures

See php-01-no-iconv.patch for the gory details. Fixes:
http://autobuild.buildroot.net/results/1c9/1c9bdfe55288430dca80a1bb514b85353d2f1c54/



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>