e1000: check on netif_running() before calling e1000_up()

When the device is not up, the call to 'e1000_up()' from the error handling path
of 'e1000_set_ringparam()' causes a kernel oops with a null-pointer
dereference. The null-pointer dereference is triggered in function
'e1000_alloc_rx_buffers()' at line 'buffer_info = &rx_ring->buffer_info[i]'.

This bug was reported by COD, a tool for testing kernel module binaries I am
building. This bug was also detected by KFI from Dr. Kai Cong.

This patch fixes the bug by checking on 'netif_running()' before calling
'e1000_up()' in 'e1000_set_ringparam()'.

Signed-off-by: Bo Chen <chenbo@pdx.edu>
Acked-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>