ippool: Correctly compute size of static pool

* we have to use stataddr, not addr (dynamic)
* we have to multiply the length of the address by 8 to get its bit length
* we can simplify the -1 +1 logic (like dynamic)

Change-Id: I174102051bef95f7df34b7d7c480a00ae408be7d
Fixes: Coverity CID#174189
diff --git a/lib/ippool.c b/lib/ippool.c
index 55a41d0..a9a64be 100644
--- a/lib/ippool.c
+++ b/lib/ippool.c
@@ -240,7 +240,7 @@
 		stataddr = stat->addr;
 		stataddrprefixlen = stat->prefixlen;
 
-		statsize = (1 << (addr.len - stataddrprefixlen + 1)) -1;
+		statsize = (1 << (stataddr.len*8 - stataddrprefixlen));
 		if (statsize > IPPOOL_STATSIZE)
 			statsize = IPPOOL_STATSIZE;
 	}