ppp: use vmalloc_array() to simplify code

Remove array_size() calls and replace vmalloc() with vmalloc_array() in
bsd_alloc().

vmalloc_array() is also optimized better, resulting in less instructions
being used.

Signed-off-by: Qianfeng Rong <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ppp/bsd_comp.c

···
  * Allocate space for the dictionary. This may be more than one page in
  * length.
  */
-    db->dict = vmalloc(array_size(hsize, sizeof(struct bsd_dict)));
+    db->dict = vmalloc_array(hsize, sizeof(struct bsd_dict));
     if (!db->dict)
       {
 	bsd_free (db);
···
  */
     else
       {
-        db->lens = vmalloc(array_size(sizeof(db->lens[0]), (maxmaxcode + 1)));
+        db->lens = vmalloc_array(maxmaxcode + 1, sizeof(db->lens[0]));
 	if (!db->lens)
 	  {
 	    bsd_free (db);