spi: stm32: fix accidential revert to byte-sized transfer splitting

Commit 6f48655 ("spi: stm32: renaming of spi_master into
spi_controller") included an accidential reverted of a change added in
commit 1e49291 ("spi: stm32: split large transfers based on word
size instead of bytes").

This breaks large SPI transfers with word sizes > 8 bits, which are
e.g. common when driving MIPI DBI displays.

Fix this by using `spi_split_transfers_maxwords()` instead of
`spi_split_transfers_maxsize()`.

Fixes: 6f48655 ("spi: stm32: renaming of spi_master into spi_controller")
Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de>
Link: https://lore.kernel.org/r/20230816145237.3159817-1-l.goehrs@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: hnez

drivers/spi/spi-stm32.c

@@ -1001,9 +1001,9 @@ static int stm32_spi_prepare_msg(struct spi_controller *ctrl,
 	if (spi->cfg->set_number_of_data) {
 		int ret;
 
-		ret = spi_split_transfers_maxsize(ctrl, msg,
-						  STM32H7_SPI_TSIZE_MAX,
-						  GFP_KERNEL | GFP_DMA);
+		ret = spi_split_transfers_maxwords(ctrl, msg,
+						   STM32H7_SPI_TSIZE_MAX,
+						   GFP_KERNEL | GFP_DMA);
 		if (ret)
 			return ret;
 	}