trivial: remove obscure division-assignment operator

In utc_mkdate() we find the interesting statement
        val = timestamp /= 60;
which not only calculates timestamp / 60, but also overwrites
timestamp with the new value. However, timestamp is never used
in the remainder of the function, because the whole point is to
switch to 32-bit types. Thus, replace the division-assignment
by a simple division operator to avoid head-scratching.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/time.c

@@ -56,7 +56,7 @@ void utc_mkdate(timestamp_t timestamp, struct tm *tm)
 
 	/* minutes since 1900 */
 	tm->tm_sec = timestamp % 60;
-	val = timestamp /= 60;
+	val = timestamp / 60;
 
 	/* Do the simple stuff */
 	tm->tm_min = val % 60;