spi: mux: set ctlr->bits_per_word_mask

Like other SPI controller flags, bits_per_word_mask may be used by a
peripheral driver, so it needs to reflect the capabilities of the
underlying controller.
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240708-spi-mux-fix-v1-3-6c8845193128@baylibre.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-mux.c

@@ -158,6 +158,7 @@ static int spi_mux_probe(struct spi_device *spi)
 	/* supported modes are the same as our parent's */
 	ctlr->mode_bits = spi->controller->mode_bits;
 	ctlr->flags = spi->controller->flags;
+	ctlr->bits_per_word_mask = spi->controller->bits_per_word_mask;
 	ctlr->transfer_one_message = spi_mux_transfer_one_message;
 	ctlr->setup = spi_mux_setup;
 	ctlr->num_chipselect = mux_control_states(priv->mux);