netfilter: ebtables: Use vmalloc_array() to improve code

netfilter: ebtables: Use vmalloc_array() to improve code

Remove array_size() calls and replace vmalloc() with vmalloc_array() to
simplify the code.  vmalloc_array() is also optimized better, uses fewer
instructions, and handles overflow more concisely[1].

[1]: https://lore.kernel.org/lkml/abc66ec5-85a4-47e1-9759-2f60ab111971@vivo.com/
Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Signed-off-by: Florian Westphal <fw@strlen.de>