spi: dw-mid: fix FIFO size

The FIFO size is 40 accordingly to the specifications, but this means 0x40,
i.e. 64 bytes. This patch fixes the typo and enables FIFO size autodetection
for Intel MID devices.

Fixes: 7063c0d942a1 (spi/dw_spi: add DMA support)
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

drivers/spi/spi-dw-mid.c

@@ -271,7 +271,6 @@ int dw_spi_mid_init(struct dw_spi *dws)
 	iounmap(clk_reg);
 
 	dws->num_cs = 16;
-	dws->fifo_len = 40;	/* FIFO has 40 words buffer */
 
 #ifdef CONFIG_SPI_DW_MID_DMA
 	dws->dma_priv = kzalloc(sizeof(struct mid_dma), GFP_KERNEL);