Add src to mypy_path in .mypy.ini

Add src to mypy_path to get rid of lots of missing import warnings.

Signed-off-by: per.held@arm.com
Change-Id: I4ed1a08cfe185aa956c6408fefa5aadeb567d4c1

Author: perheld

.mypy.ini

@@ -24,7 +24,7 @@ files =
     test,
     util
 
-mypy_path = executorch
+mypy_path = executorch,src
 
 [mypy-executorch.backends.*]
 follow_untyped_imports = True