ixp4xx_eth: fix compile-testing

Change the driver to use portable integer types to avoid warnings
during compile testing, including:

drivers/net/ethernet/xscale/ixp4xx_eth.c:721:21: error: cast to 'u32 *' (aka 'unsigned int *') from smaller integer type 'int' [-Werror,-Wint-to-pointer-cast]
        memcpy_swab32(mem, (u32 *)((int)skb->data & ~3), bytes / 4);
                           ^
drivers/net/ethernet/xscale/ixp4xx_eth.c:963:12: error: incompatible pointer types passing 'u32 *' (aka 'unsigned int *') to parameter of type 'dma_addr_t *' (aka 'unsigned long long *') [-Werror,-Wincompatible-pointer-types]
                                              &port->desc_tab_phys)))
                                              ^~~~~~~~~~~~~~~~~~~~
include/linux/dmapool.h:27:20: note: passing argument to parameter 'handle' here
                     dma_addr_t *handle);
                                 ^

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>