Optimize ST7796 driver: Use bulk SPI transfers and blocking DMA for higher framerate

lib/st7796/st7796.h

@@ -233,6 +233,21 @@ void st7796_set_cursor(uint16_t x, uint16_t y);
  */
 void st7796_write(const uint16_t *data, size_t len);
 
+/**
+ * @brief Write raw buffer data directly to display
+ * 
+ * Writes a buffer of bytes directly to the display without any
+ * conversion or byte swapping. This function assume the data is
+ * already in the correct format (Big-Endian RGB565) for the display.
+ * 
+ * This is significantly faster for large block transfers than
+ * st7796_write() as it uses a single SPI transaction.
+ * 
+ * @param data Pointer to raw byte buffer
+ * @param len Number of bytes to send
+ */
+void st7796_write_raw(const uint8_t *data, size_t len);
+
 /**
  * @brief Draw a single pixel at specified coordinates
  *