Fix two minor lint errors (cppcheck)

Fix two minor errors reported by cppcheck:

In module/zfs/abd.c (abd_get_offset_impl), add non-NULL
assertion to prevent NULL dereference warning.

In module/zfs/arc.c (l2arc_write_buffers), change 'try'
variable to 'pass' to avoid C++ reserved word.

Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Colm Buckley <[email protected]>
Closes #11507

module/zfs/abd.c

@@ -526,6 +526,7 @@ abd_get_offset_impl(abd_t *abd, abd_t *sabd, size_t off, size_t size)
 		abd = abd_get_offset_scatter(abd, sabd, off);
 	}
 
+	ASSERT3P(abd, !=, NULL);
 	abd->abd_size = size;
 	abd->abd_parent = sabd;
 	(void) zfs_refcount_add_many(&sabd->abd_children, abd->abd_size, abd);

module/zfs/arc.c

@@ -9080,17 +9080,17 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
 	/*
 	 * Copy buffers for L2ARC writing.
 	 */
-	for (int try = 0; try < L2ARC_FEED_TYPES; try++) {
+	for (int pass = 0; pass < L2ARC_FEED_TYPES; pass++) {
 		/*
-		 * If try == 1 or 3, we cache MRU metadata and data
+		 * If pass == 1 or 3, we cache MRU metadata and data
 		 * respectively.
 		 */
 		if (l2arc_mfuonly) {
-			if (try == 1 || try == 3)
+			if (pass == 1 || pass == 3)
 				continue;
 		}
 
-		multilist_sublist_t *mls = l2arc_sublist_lock(try);
+		multilist_sublist_t *mls = l2arc_sublist_lock(pass);
 		uint64_t passed_sz = 0;
 
 		VERIFY3P(mls, !=, NULL);