*: add empty array of YANG modules

*: add empty array of YANG modules

FRR_DAEMON_INFO should now contain an array of 'frr_yang_module_info'
structures describing the YANG modules implemented by the daemon.

This array will be used by frr_init() function to load all YANG modules
and initialize the northbound callbacks during the daemon initialization.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>