docs/bpf: Fix sample code in MAP_TYPE_ARRAY docs

Remove mistaken & from code example in MAP_TYPE_ARRAY docs

Fixes: 1cfa97b3 ("bpf, docs: Document BPF_MAP_TYPE_ARRAY")
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://lore.kernel.org/r/20221115095910.86407-1-donald.hunter@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Documentation/bpf/map_array.rst

@@ -119,7 +119,7 @@ This example BPF program shows how to access an array element.
             index = ip.protocol;
             value = bpf_map_lookup_elem(&my_map, &index);
             if (value)
-                    __sync_fetch_and_add(&value, skb->len);
+                    __sync_fetch_and_add(value, skb->len);
 
             return 0;
     }