synthesis: fix review comments

Signed-off-by: Øyvind Harboe <[email protected]>

Author: oharboe

flow/designs/asap7/aes/README.md

@@ -3,9 +3,16 @@
 For large designs, it can be useful to split synthesis for the
 major blocks and combine the synthesized result.
 
+SYNTH_HIERARCHICAL=1 and MAX_UNGROUP_SIZE can be used to adjust which
+modules are flattened and which are kept.
+
+A module that is not flattened, can be built separately without any
+loss in quality of results and combined as shown below. The module
+that is built separately be built with and without SYNTH_HIERARCHICAL=1.
+
 1. Synthesize aes_key_expand_128 module
 
-       make DESIGN_CONFIG=designs/asap7/aes/config.mk LOW_VARIANT=blackbox clean_synth synth
+       make DESIGN_CONFIG=designs/asap7/aes/config.mk FLOW_VARIANT=blackbox clean_synth synth
 2. Synthesize top module, which could happen in parallel to 1 but with aes_key_expand_128 blacklisted:
 
        make DESIGN_CONFIG=designs/asap7/aes/config.mk FLOW_VARIANT=top clean_synth synth