sandbox: Add LCD driver

Add a simple LCD driver which uses SDL to display the image. We update the
image regularly, while still providing for reasonable performance.

Adjust the common lcd code to support sandbox.

For command-line runs we do not want the LCD to be displayed, so add a
--show_lcd option to enable it.

Tested-by: Che-Liang Chiou <clchiou@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/include/asm/state.h

@@ -41,6 +41,7 @@ struct sandbox_state {
 	bool read_state;		/* Read sandbox state on startup */
 	bool write_state;		/* Write sandbox state on exit */
 	bool ignore_missing_state_on_read;	/* No error if state missing */
+	bool show_lcd;			/* Show LCD on start-up */
 
 	/* Pointer to information for each SPI bus/cs */
 	struct sandbox_spi_info spi[CONFIG_SANDBOX_SPI_MAX_BUS]

arch/sandbox/include/asm/u-boot-sandbox.h

@@ -25,4 +25,7 @@ int sandbox_main_loop_init(void);
 
 int cleanup_before_linux(void);
 
+/* drivers/video/sandbox_sdl.c */
+int sandbox_lcd_sdl_early_init(void);
+
 #endif	/* _U_BOOT_SANDBOX_H_ */