staging: et131x: zero allocation of fbr to prevent random address access

If et131x_rx_dma_memory_alloc() allocates rx_ring->fbr[0] but fails to
allocate rx_ring->fbr[1], this leaves fbr[0]->ring_virtaddr with the
possibility of being accessed in et131x_rx_dma_memory_free() as it
contains a random value, potentially causing an oops.

Fix this by zeroing the fbr memory on allocation. Subsequent frees of
this fbr memory explicitly zeros the ring_virtaddr value.

Reported-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Mark Einon <mark.einon@gmail.com>
staging: et131x: don't cast a void* to a struct pointer

Casting a void* popinter to a struct pointer is unnecessary, don't do
it.

Signed-off-by: Mark Einon <mark.einon@gmail.com>
staging: et131x: Add space after { in pci ID table

Signed-off-by: Mark Einon <mark.einon@gmail.com>
staging: et131x: Remove unnecessary defines to enable driver PM

The Power Management functions can be conditional by assigning pm ops
directly to .driver.pm, instead of using #ifdef's, saving some lines of
code.

Reported-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Mark Einon <mark.einon@gmail.com>