enic: free all rq buffs when allocation fails

When allocation of all RQs fail, we do not free previously allocated buffers,
before returning error. This causes memory leak.

This patch fixes this by calling vnic_rq_clean(), which frees all the rq
buffers.

Signed-off-by: Govindarajulu Varadarajan <_govind@gmx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>