ASoC: Remove unneeded forward reference to WM8753 SPI implementation

#include "wm8753.h"

#ifdef CONFIG_SPI_MASTER

static struct spi_driver wm8753_spi_driver;

static int wm8753_spi_write(struct spi_device *spi, const char *data, int len);

#endif

static int caps_charge = 2000;

module_param(caps_charge, int, 0);

MODULE_PARM_DESC(caps_charge, "WM8753 cap charge time (msecs)");