package/collectd: fix build with amqp

collectd unconditionally uses amqp_ssl_socket.h since version 5.11.0 and
https://github.com/collectd/collectd/commit/e4808ad138de362fab5efa09648fbc101f97bd76

Fixes:
 - http://autobuild.buildroot.org/results/525abe0a5cca81ff517c9c07c092d85160c7eb62



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>