package/hidapi: depends on NPTL threads

hidapi use NPTL threads functions like pthread_barrier_wait() and
pthread_barrier_destroy(). So the dependency on threads support
doesn't come from libusb package but by hidapi itself.

Fixes:
[microblaze]
http://autobuild.buildroot.net/results/f7e/f7e778562aa1a65ba46f3b2f705d13ace8870805
[m68k]
http://autobuild.buildroot.net/results/2ec/2ecd240ccb15de76017942a8960faac6b3f973b4



Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>