spec_calibrating_poll was using ep_get_deltas instead of
spec_read_calibration_data, like freestanding-wrapper.c does in wrpc-sw.
The whole spec-calibration.c is obsolete, since it should simply be a
wrapper for wrpc-sw functions defined in
ptp-noposix/libposix/freestanding-wrapper.c
Signed-off-by: Aurelio Colosimo <aurelio@aureliocolosimo.it>