ata: sata_rcar: Fix compilation warning

When compiling with clang and W=1, the following warning is generated:

drivers/ata/sata_rcar.c:878:15: error: cast to smaller integer type
'enum sata_rcar_type' from 'const void *'
[-Werror,-Wvoid-pointer-to-enum-cast]
        priv->type = (enum sata_rcar_type)of_device_get_match_data(dev);
                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix this by using a cast to unsigned long to match the "void *" type
size returned by of_device_get_match_data().

Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>