[opcodes] ARC + PPC: Fix -Walloc-size warnings

Recently, -Walloc-size warnings started to kick in. Fix these two
calloc() calls to match the intended usage pattern.

opcodes/ChangeLog:

	* arc-dis.c (init_arc_disasm_info): Fix calloc() call.
	* ppc-dis.c (powerpc_init_dialect): Ditto.

opcodes/arc-dis.c

@@ -147,7 +147,7 @@ static bool
 init_arc_disasm_info (struct disassemble_info *info)
 {
   struct arc_disassemble_info *arc_infop
-    = calloc (sizeof (*arc_infop), 1);
+    = calloc (1, sizeof (*arc_infop));
 
   if (arc_infop == NULL)
     return false;

opcodes/ppc-dis.c

@@ -348,7 +348,7 @@ powerpc_init_dialect (struct disassemble_info *info)
 {
   ppc_cpu_t dialect = 0;
   ppc_cpu_t sticky = 0;
-  struct dis_private *priv = calloc (sizeof (*priv), 1);
+  struct dis_private *priv = calloc (1, sizeof (*priv));
 
   if (priv == NULL)
     return;