spi: s3c64xx: fix timeout counters in flush_fifo

In the s3c64xx_flush_fifo() code, the loops counter is post-decremented
in the do { } while(test && loops--) condition. This means the loops is
left at the unsigned equivalent of -1 if the loop times out. The test
after will never pass as if tests for loops == 0.

Signed-off-by: Ben Dooks <[e-mail]>
Fixes: 230d42d422e7 ("spi: Add s3c64xx SPI Controller driver")
Reviewed-by: Andi Shyti <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spi-s3c64xx.c

···
 	loops = msecs_to_loops(1);
 	do {
 		val = readl(regs + S3C64XX_SPI_STATUS);
-	} while (TX_FIFO_LVL(val, sdd) && loops--);
+	} while (TX_FIFO_LVL(val, sdd) && --loops);
 
 	if (loops == 0)
 		dev_warn(&sdd->pdev->dev, "Timed out flushing TX FIFO\n");
···
 			readl(regs + S3C64XX_SPI_RX_DATA);
 		else
 			break;
-	} while (loops--);
+	} while (--loops);
 
 	if (loops == 0)
 		dev_warn(&sdd->pdev->dev, "Timed out flushing RX FIFO\n");