MLBEDSW-3573: Document CSV files

Added references to performance CSVs and documented per-layer performance.

Also removed a space that caused black in pre-commit to fail.

Change-Id: Ia20cb381654cc6344c68bcaad0a7dfc517d55e63
Signed-off-by: wilisa01 <william.isaksson@arm.com>
diff --git a/ethosu/vela/debug_database.py b/ethosu/vela/debug_database.py
index c1389e5..ac4ef17 100644
--- a/ethosu/vela/debug_database.py
+++ b/ethosu/vela/debug_database.py
@@ -61,7 +61,7 @@
             [uid, str(op.type), op.kernel.width, op.kernel.height, ofm_shape[-2], ofm_shape[-3], ofm_shape[-1]]
         )
 
-    # Ops are added when their type changes, and after optimisation. If an op was already 
+    # Ops are added when their type changes, and after optimisation. If an op was already
     # added before optimisation was finished it will only be added again if it's entry
     # has changed in any way from it's previous entry.
     @classmethod