[reggen] Fix indentation in ip_block.py

Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>
diff --git a/util/reggen/ip_block.py b/util/reggen/ip_block.py
index 5865d04..600c3f4 100644
--- a/util/reggen/ip_block.py
+++ b/util/reggen/ip_block.py
@@ -253,7 +253,7 @@
                                 'scan_reset field of ' + what)
 
         scan_en = check_bool(rd.get('scan_en', False),
-                                'scan_en field of ' + what)
+                             'scan_en field of ' + what)
 
         # Check that register blocks are in bijection with device interfaces
         reg_block_names = reg_blocks.keys()