spi/dw_spi: remove the un-necessary flush()

The flush() is used to drain all the left data in rx fifo, currently
is is always called together with disabling hw. But from spec, disabling
hw will also reset all the fifo, so flush() is not needed.
Signed-off-by: NAlek Du <alek.du@intel.com>
Signed-off-by: NFeng Tang <feng.tang@intel.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

drivers/spi/dw_spi.c

@@ -173,17 +173,6 @@ static void wait_till_not_busy(struct dw_spi *dws)
 		"DW SPI: Status keeps busy for 5000us after a read/write!\n");
 }
 
-static void flush(struct dw_spi *dws)
-{
-	while (dw_readw(dws, sr) & SR_RF_NOT_EMPT) {
-		dw_readw(dws, dr);
-		cpu_relax();
-	}
-
-	wait_till_not_busy(dws);
-}
-
-
 static int dw_writer(struct dw_spi *dws)
 {
 	u16 txw = 0;
@@ -297,8 +286,7 @@ static void giveback(struct dw_spi *dws)
 
 static void int_error_stop(struct dw_spi *dws, const char *msg)
 {
-	/* Stop and reset hw */
-	flush(dws);
+	/* Stop the hw */
 	spi_enable_chip(dws, 0);
 
 	dev_err(&dws->master->dev, "%s\n", msg);
@@ -800,7 +788,6 @@ static void spi_hw_init(struct dw_spi *dws)
 	spi_enable_chip(dws, 0);
 	spi_mask_intr(dws, 0xff);
 	spi_enable_chip(dws, 1);
-	flush(dws);
 
 	/*
 	 * Try to detect the FIFO depth if not set by interface driver,