buildroot

ntp: add patch to fix -fPIC issue

This commit adds a patch that fixes the build on AArch64 and MIPS of the
ntp package, which was caused by some parts of ntp being built without
-fPIC.

Fixes:

  [aarch64] http://autobuild.buildroot.net/results/866b1d28595efd8b6becf83d0a64b596538d58b0
  [mips]    http://autobuild.buildroot.net/results/c2a945855172970736a8ffea9c564f029a023344

Thanks to Romain Naour for the initial analysis.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>