ti: ethernet: davinci: Fix cast to int warnings

Now that we can compile test this driver on 64-bit hosts, we get some
warnings about how a pointer/address is written/read to/from a register
(sw_token). Fix this by doing the appropriate conversions, we cannot
possibly have the driver work on 64-bit hosts the way the tokens are
managed though, since the registers being written to a 32-bit only.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>