chan_dahdi: wrap include file which is not present on BSD systems in #ifdef

The sys/sysmacros.h include file does not exist in BSD systems and
is not required to build this module there.
Since an "#if defined(__NetBSD__) || defined(__FreeBSD__)" section
already exist I moved that include line inside it's #else branch.

ASTERISK-27343 #close

Change-Id: Ibfb64f4e9a0ce8b6eda7a7695cfe57916f175dc1