Since the hal client is called in two places
(arch-wrs/wrs-calibration.c and time-wrs/wrs-time.c), put what is common
in the general include file provided by arch-wrs. Indeed this file
should be moved to arch-wrs/include (will be done in one of the
next commits).

Signed-off-by: Aurelio Colosimo <aurelio@aureliocolosimo.it>