qed: Add cleanup in qed_slowpath_start()

If qed_mcp_send_drv_version() fails, no cleanup is executed, leading to
memory leaks. To fix this issue, introduce the label 'err4' to perform the
cleanup work before returning the error.

Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
Acked-by: Sudarsana Reddy Kalluru <skalluru@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>