Hi using this little trick you can easily remove wordpress logo and related sub menus from admin panel bar,
The only trick you need to do is just copy and paste below code on the
wp-content/thems/yourThemeName/function.php file of your theme.

add_action('admin_bar_menu', 'remove_wp_logo', 999);
function remove_wp_logo( $wp_admin_bar ) {
$wp_admin_bar->remove_node('wp-logo');
}

Enjoy :)