staging: wilc1000: linux_wlan_spi: correct types

linux_spi_write(), linux_spi_read(), linux_spi_write_read():

    nwi->io_func.u.spi.spi_tx = linux_spi_write;
    nwi->io_func.u.spi.spi_rx = linux_spi_read;
    nwi->io_func.u.spi.spi_trx = linux_spi_write_read;

are expected to accept arguments of 'u8 *', u32 types:

    struct {
        int (*spi_max_speed)(void);
        int (*spi_tx)(u8 *, u32);
        int (*spi_rx)(u8 *, u32);
        int (*spi_trx)(u8 *, u8 *, u32);
    } spi;

However, linux_spi_read() and linux_spi_write_read() do not do this,
they use 'unsigned char *' and 'unsigned long' instead.

Changed the types of their arguments to satisfy the expectations.

Signed-off-by: Stanislav Kholmanskikh <kholmanskikh.s.s@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>