fchmodat: fix handling of flags
fchmodat: fix handling of flags

The Linux syscall takes 3 args, not 4.  We have to process flags in
userspace ourselves.

Signed-off-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@gentoo.org>

joel-porquet/tsar-uclibc,joel-porquet/tsar-uclibc,joel-porquet/tsar-uclibc,joel-porquet/tsar-uclibc