posix: clock: fix potential int32_t overflow in __z_clock_nanosleep

As k_sleep returns int32_t, there is a possibility for integer overflow
during conversion from milliseconds to nanoseconds.

Signed-off-by: Ilya Tagunov <[email protected]>

Author: tagunil

lib/posix/options/clock.c

@@ -220,7 +220,7 @@ static int __z_clock_nanosleep(clockid_t clock_id, int flags, const struct times
 	    unlikely(rqtp->tv_sec >= ULLONG_MAX / NSEC_PER_SEC)) {
 
 		ns = rqtp->tv_nsec + NSEC_PER_SEC
-			+ k_sleep(K_SECONDS(rqtp->tv_sec - 1)) * NSEC_PER_MSEC;
+			+ (uint64_t)k_sleep(K_SECONDS(rqtp->tv_sec - 1)) * NSEC_PER_MSEC;
 	} else {
 		ns = (uint64_t)rqtp->tv_sec * NSEC_PER_SEC + rqtp->tv_nsec;
 	}