drivers/net: add missing __devexit_p() annotations

Drivers that refer to a __devexit function in an operations
structure need to annotate that pointer with __devexit_p so
replace it with a NULL pointer when the section gets discarded.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>