irrespective of the setting of lem_rx_process_limit, while
	giving a chance to the taskqueue scheduler to act after
	each chunk.
	This makes lem_rxeof similar to the one in if_em.c and if_igb.c .

if_lem.c and if_em.c: add a sysctl to manually configure the
	'itr' moderation register.

Approved by:	Jack Vogel