mtd: spi-nor: improve wait-till-ready timeout loop

There are a few small issues with the timeout loop in
spi_nor_wait_till_ready():

 * The first operation should not be a reschedule; we should check the
   status register at least once to see if we're complete!

 * We should check the status register one last time after declaring the
   deadline has passed, to prevent a premature timeout error (this is
   theoretically possible if we sleep for a long time after the previous
   status register check).

 * Add an error message, so it's obvious if we ever hit a timeout.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Acked-by: Huang Shijie <shijie.huang@intel.com>
Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

drivers/mtd/spi-nor/spi-nor.c

@@ -202,19 +202,24 @@ static int spi_nor_ready(struct spi_nor *nor)
 static int spi_nor_wait_till_ready(struct spi_nor *nor)
 {
 	unsigned long deadline;
-	int ret;
+	int timeout = 0, ret;
 
 	deadline = jiffies + MAX_READY_WAIT_JIFFIES;
 
-	do {
-		cond_resched();
+	while (!timeout) {
+		if (time_after_eq(jiffies, deadline))
+			timeout = 1;
 
 		ret = spi_nor_ready(nor);
 		if (ret < 0)
 			return ret;
 		if (ret)
 			return 0;
-	} while (!time_after_eq(jiffies, deadline));
+
+		cond_resched();
+	}
+
+	dev_err(nor->dev, "flash operation timed out\n");
 
 	return -ETIMEDOUT;
 }