lcd: spi lcd support transmit lsb first

Closes https://github.com/espressif/esp-idf/issues/8790

components/esp_lcd/include/esp_lcd_panel_io.h

@@ -98,7 +98,8 @@ typedef struct {
         unsigned int dc_as_cmd_phase: 1; /*!< D/C line value is encoded into SPI transaction command phase */
         unsigned int dc_low_on_data: 1;  /*!< If this flag is enabled, DC line = 0 means transfer data, DC line = 1 means transfer command; vice versa */
         unsigned int octal_mode: 1;      /*!< transmit with octal mode (8 data lines), this mode is used to simulate Intel 8080 timing */
-    } flags;
+        unsigned int lsb_first: 1;       /*!< transmit LSB bit first */
+    } flags; /*!< Extra flags to fine-tune the SPI device */
 } esp_lcd_panel_io_spi_config_t;
 
 /**

components/esp_lcd/src/esp_lcd_panel_io_spi.c

@@ -72,7 +72,8 @@ esp_err_t esp_lcd_new_panel_io_spi(esp_lcd_spi_bus_handle_t bus, const esp_lcd_p
     ESP_GOTO_ON_FALSE(spi_panel_io, ESP_ERR_NO_MEM, err, TAG, "no mem for spi panel io");
 
     spi_device_interface_config_t devcfg = {
-        .flags = SPI_DEVICE_HALFDUPLEX, // only use TX path, so half duplex is enough
+        // currently the driver only supports TX path, so half duplex is enough
+        .flags = SPI_DEVICE_HALFDUPLEX | (io_config->flags.lsb_first ? SPI_DEVICE_TXBIT_LSBFIRST : 0),
         .clock_speed_hz = io_config->pclk_hz,
         .mode = io_config->spi_mode,
         .spics_io_num = io_config->cs_gpio_num,