samples/tests: Convert use of %ll{u,d} to PRI{u,d}64

Move to using PRIu64/PRId64 instead of %llu/%lld since on
native_posix_64 the uint64_t/int64_t type is defined in terms of 'long
int' and not 'long long int'.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>