davinci_cpdma: export symbols used by other drivers

The davinci_emac driver can be a module, so the symbols
it needs from the cpdma driver must be exported.

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>