memif: Use log_debug for clib_file_add and clib_file_del
memif: Use log_debug for clib_file_add and clib_file_del

It is more appropriate to use log_debug instead of log_warn when inoking
clib_file_add and clib_file_del.

Type: fix

Signed-off-by: Steven Luong <a748ea44ad7b179c2313a856d44e1e4eb39869bb@cisco.com>
Change-Id: I544d97037cfca3f22ce94242aef0c7b0fea2fa9b

FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp