Zebra: Handle RMAC add/delete operation and add fpm_mac_info_t

Zebra: Handle RMAC add/delete operation and add fpm_mac_info_t

- Define a hook "zebra_mac_update" which can be registered by multiple
  data plane components (e.g. FPM, dplane).

DEFINE_HOOK(zebra_rmac_update, (zebra_mac_t *rmac, zebra_l3vni_t *zl3vni, bool
	    delete, const char *reason), (rmac, zl3vni, delete, reason))

- While performing RMAC add/delete for an L3VNI, call "zebra_mac_update" hook.

- This hook call triggers "zfpm_trigger_rmac_update". In this function, we do a
  lookup for the RMAC in fpm_mac_info_table. If already present, this node is
  updated with the latest RMAC info. Else, a new fpm_mac_info_t node is created
  and inserted in the queue and hash data structures.

Signed-off-by: Ameya Dharkar <adharkar@vmware.com>