bnx2x: fix page fault following EEH recovery

In the last step of the EEH recovery process, the EEH driver calls into
bnx2x_io_resume() to re-initialize the NIC hardware via the function
bnx2x_nic_load().  If an error occurs during bnx2x_nic_load(), OS and
hardware resources are released and an error code is returned to the
caller.  When called from bnx2x_io_resume(), the return code is ignored
and the network interface is brought up unconditionally.  Later attempts
to send a packet via this interface result in a page fault due to a null
pointer reference.

This patch checks the return code of bnx2x_nic_load(), prints an error
message if necessary, and does not enable the interface.

Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
Reviewed-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>