[docker-lldp] limit privileged flag for lldp container (#15830)

#### Why I did it
HLD implementation: Container Hardening (sonic-net/SONiC#1364)
##### Work item tracking
- Microsoft ADO **(number only)**: 14807420

#### How I did it
Reduce linux capabilities in privileged flag, retain NET_ADMIN capability

rules/docker-lldp.mk

@@ -28,7 +28,7 @@ SONIC_DOCKER_DBG_IMAGES += $(DOCKER_LLDP_DBG)
 SONIC_INSTALL_DOCKER_DBG_IMAGES += $(DOCKER_LLDP_DBG)
 
 $(DOCKER_LLDP)_CONTAINER_NAME = lldp
-$(DOCKER_LLDP)_RUN_OPT += --privileged -t
+$(DOCKER_LLDP)_RUN_OPT += -t --cap-add=NET_ADMIN
 $(DOCKER_LLDP)_RUN_OPT += -v /etc/sonic:/etc/sonic:ro
 $(DOCKER_LLDP)_RUN_OPT += -v /etc/timezone:/etc/timezone:ro