compositor-fbdev: set fb device info upon the first run.

This attempts to wake up secondary framebuffer devices
(/dev/fb1 and up) as usually these devices start powered off, and
the FBIOPUT_VSCREENINFO ioctl turns it on. This was tested on a
qemu system with the options:

-vga none -device VGA,id=video0 -device secondary-vga,id=video1 \
-device secondary-vga,id=video2

Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

libweston/compositor-fbdev.c

@@ -384,6 +384,14 @@ fbdev_frame_buffer_open(const char *fb_dev,
 		return -1;
 	}
 
+	/* Attempt to wake up the framebuffer device, needed for secondary
+	 * framebuffer devices */
+	if (fbdev_set_screen_info(fd, screen_info) < 0) {
+		weston_log("Failed to set mode settings. "
+		           "Attempting to open output anyway.\n");
+	}
+
+
 	return fd;
 }