You can do this by putting your piece of code in a function and call it where required just like any template tag.
<?php
function the_logo(){ ?>
<div id="logo">
<?php if( get_theme_mod( 'mlwd_logo_image') ) : ?>
<img src="https://wordpress.stackexchange.com/questions/337491/<?php echo esc_url(get_theme_mod("mlwd_logo_image')); ?>" alt="Logo"/>
<?php else: ?>
<h1>
<a href="<?php echo home_url(); ?>" title="<?php bloginfo('name'); ?>">
<?php bloginfo('name'); ?><?php echo $langblog;?>
</a>
</h1>
<p>
<?php bloginfo('description'); ?><?php echo $langblog;?>
</p>
<?php endif ?>
</div>
<?php } ?>
And the header would look like
<header id="header" class="clear" role="banner">
<div class="column column-one four-quarter">
<div class="container clear">
<?php if( get_theme_mod( 'mlwd_logo_layout', 'insideheader' ) == 'insideheader' ) && get_theme_mod('mlwd_logo_position_y', 'top') :
// Piece of code from code.php file
the_logo();
endif ?>
</div>
</div>
<div class="column column-two four-quarter">
<div class="container clear">
<?php if( get_theme_mod( 'mlwd_logo_layout', 'insideheader' ) == 'insideheader' ) && get_theme_mod('mlwd_logo_position_y', 'bottom') :
// Piece of code from code.php file
the_logo();
endif ?>
</div>
</div>
</header>
I hope this may be helpful,