mtd: spi-nor: Support controllers with limited TX FIFO size

Some SPI controllers can't write nor->page_size bytes in a single
step because their TX FIFO is too small.

Allow nor->write() to return a size that is smaller than the requested
write size to gracefully handle this case.

Signed-off-by: Yogesh Gaur <yogeshnarayan.gaur@nxp.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>

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

@@ -1756,13 +1756,6 @@ static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
 			goto write_err;
 		*retlen += written;
 		i += written;
-		if (written != page_remain) {
-			dev_err(nor->dev,
-				"While writing %zu bytes written %zd bytes\n",
-				page_remain, written);
-			ret = -EIO;
-			goto write_err;
-		}
 	}
 
 write_err: