net: ethernet: bgmac: add dma_dev pointer

The dma buffer allocation, etc references a dma_dev device pointer from
the bcma core.  In anticipation of removing the bcma requirement for
this driver, these must be changed to not reference that struct.  Add a
dma_dev device pointer to the bgmac stuct and reference that instead.

Signed-off-by: Jon Mason <jon.mason@broadcom.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>