libply: Fix kallsym lookup for split 64bit address space

Fixup the kallsym sort-compare function.

Sorting the kallsyms breaks when comparing addresses that are more than
INT_MAX bytes apart. The could break e.g. the stack or caller output.

Seen on a ppc64 Linux kernel where kernel memory is divided into
different address regions. Kernel modules are placed at
0xc0000100xxxxxxx and the core kernel at 0xc000000xxxxxxx.

Signed-off-by: Anders Grahn <anders.grahn@westermo.com>

Author: Anders Grahn

src/libply/aux/kallsyms.c

@@ -223,7 +223,12 @@ static int ksym_sort_cmp(const void *_a, const void *_b)
 {
 	const struct ksym *a = _a, *b = _b;
 
-	return a->addr - b->addr;
+	if (a->addr > b->addr)
+		return 1;
+	else if (a->addr < b->addr)
+		return -1;
+	else
+		return 0;
 }
 
 static int ksyms_cache_sort(struct ksyms *ks)