[PATCH] mISDN: avoid arch specific __builtin_return_address call

[Joe Perches]

On Tue, 2015-01-13 at 17:10 +0100, Arnd Bergmann wrote:
> Not all architectures are able to call __builtin_return_address().
> On ARM, the mISDN code produces this warning:
> 
> hardware/mISDN/w6692.c: In function 'w6692_dctrl':
> hardware/mISDN/w6692.c:1181:75: warning: unsupported argument to '__builtin_return_address'
>   pr_debug("%s: %s dev(%d) open from %p\n", card->name, __func__,

I didn't know that tidbit. Thanks.