fpga: microchip-spi: separate data frame write routine

mpf_ops_write() function writes bitstream data to the FPGA by a smaller
frames. Introduce mpf_spi_frame_write() function which is for writing a
single data frame and use it in mpf_ops_write().

No functional changes intended.
Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20221230092922.18822-4-i.bornyakov@metrotek.ruSigned-off-by: Xu Yilun <yilun.xu@intel.com>

drivers/fpga/microchip-spi.c

@@ -280,9 +280,30 @@ static int mpf_ops_write_init(struct fpga_manager *mgr,
 	return 0;
 }
 
+static int mpf_spi_frame_write(struct mpf_priv *priv, const char *buf)
+{
+	struct spi_transfer xfers[2] = {
+		{
+			.tx_buf = &priv->tx,
+			.len = 1,
+		}, {
+			.tx_buf = buf,
+			.len = MPF_SPI_FRAME_SIZE,
+		},
+	};
+	int ret;
+
+	ret = mpf_poll_status(priv, 0);
+	if (ret < 0)
+		return ret;
+
+	priv->tx = MPF_SPI_FRAME;
+
+	return spi_sync_transfer(priv->spi, xfers, ARRAY_SIZE(xfers));
+}
+
 static int mpf_ops_write(struct fpga_manager *mgr, const char *buf, size_t count)
 {
-	struct spi_transfer xfers[2] = { 0 };
 	struct mpf_priv *priv = mgr->priv;
 	struct device *dev = &mgr->dev;
 	int ret, i;
@@ -293,19 +314,8 @@ static int mpf_ops_write(struct fpga_manager *mgr, const char *buf, size_t count
 		return -EINVAL;
 	}
 
-	xfers[0].tx_buf = &priv->tx;
-	xfers[0].len = 1;
-
 	for (i = 0; i < count / MPF_SPI_FRAME_SIZE; i++) {
-		xfers[1].tx_buf = buf + i * MPF_SPI_FRAME_SIZE;
-		xfers[1].len = MPF_SPI_FRAME_SIZE;
-
-		ret = mpf_poll_status(priv, 0);
-		if (ret >= 0) {
-			priv->tx = MPF_SPI_FRAME;
-			ret = spi_sync_transfer(priv->spi, xfers, ARRAY_SIZE(xfers));
-		}
-
+		ret = mpf_spi_frame_write(priv, buf + i * MPF_SPI_FRAME_SIZE);
 		if (ret) {
 			dev_err(dev, "Failed to write bitstream frame %d/%zu\n",
 				i, count / MPF_SPI_FRAME_SIZE);