ipv4: Fix compilation errors in fib_rebalance

This fixes

net/built-in.o: In function `fib_rebalance':
fib_semantics.c:(.text+0x9df14): undefined reference to `__divdi3'

and

net/built-in.o: In function `fib_rebalance':
net/ipv4/fib_semantics.c:572: undefined reference to `__aeabi_ldivmod'

Fixes: 0e884c78 ("ipv4: L3 hash-based multipath")
Signed-off-by: Peter Nørlund <pch@ordbogen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/fib_semantics.c

@@ -569,7 +569,7 @@ static void fib_rebalance(struct fib_info *fi)
 			upper_bound = -1;
 		} else {
 			w += nexthop_nh->nh_weight;
-			upper_bound = DIV_ROUND_CLOSEST(2147483648LL * w,
+			upper_bound = DIV_ROUND_CLOSEST_ULL((u64)w << 31,
 							    total) - 1;
 		}