dropbear: override detection of struct sockaddr_storage

Configure misdetects this as no, but the result is not used for anything.
Unfortunately it breaks the build for other packages also checking for
struct sockaddr_storage (like rsync) when using a shared config cache,
so force it to yes.

Reported-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>