spi: sirf: fix word width configuration

commit 8c328a262f ("spi: sirf: Avoid duplicate code in various
bits_per_word cases") is wrong in setting data width register of
fifo is not right, it should use sspi->word_width >> 1 to set
related bits. According to hardware spec, the mapping between
register value and data width:
0 - byte
1 - WORD
2 - DWORD

Fixes: 8c328a262f ("spi: sirf: Avoid duplicate code in various bits_per_word cases") is wrong in setting data width register of
Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

drivers/spi/spi-sirf.c

@@ -562,9 +562,9 @@ spi_sirfsoc_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
 
 	sspi->word_width = DIV_ROUND_UP(bits_per_word, 8);
 	txfifo_ctrl = SIRFSOC_SPI_FIFO_THD(SIRFSOC_SPI_FIFO_SIZE / 2) |
-					   sspi->word_width;
+					   (sspi->word_width >> 1);
 	rxfifo_ctrl = SIRFSOC_SPI_FIFO_THD(SIRFSOC_SPI_FIFO_SIZE / 2) |
-					   sspi->word_width;
+					   (sspi->word_width >> 1);
 
 	if (!(spi->mode & SPI_CS_HIGH))
 		regval |= SIRFSOC_SPI_CS_IDLE_STAT;