staging: wfx: load the firmware faster

During the loading of the firmware, the WFX_DCA_GET register provide the
number available bytes in the receiving buffer. It is not necessary to
access to the WFX_DCA_GET after sent of each firmware fragment.

This patch allows to send the firmware:
  - in 64ms instead of 130ms using SDIO bus
  - in 78ms instead of 115ms using SPI bus
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200701150707.222985-6-Jerome.Pouiller@silabs.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/fwio.c

@@ -188,15 +188,14 @@ static int upload_firmware(struct wfx_dev *wdev, const u8 *data, size_t len)
 	while (offs < len) {
 		start = ktime_get();
 		for (;;) {
-			ret = sram_reg_read(wdev, WFX_DCA_GET, &bytes_done);
-			if (ret < 0)
-				return ret;
 			now = ktime_get();
-			if (offs +
-			    DNLD_BLOCK_SIZE - bytes_done < DNLD_FIFO_SIZE)
+			if (offs + DNLD_BLOCK_SIZE - bytes_done < DNLD_FIFO_SIZE)
 				break;
 			if (ktime_after(now, ktime_add_ms(start, DCA_TIMEOUT)))
 				return -ETIMEDOUT;
+			ret = sram_reg_read(wdev, WFX_DCA_GET, &bytes_done);
+			if (ret < 0)
+				return ret;
 		}
 		if (ktime_compare(now, start))
 			dev_dbg(wdev->dev, "answer after %lldus\n",