vela: Ignore __pycache__ folders

No need for git to track those.

Signed-off-by: Michael McGeagh <michael.mcgeagh@arm.com>
Change-Id: I8fd5b8099961133a3abec111c78a4ca7a42bdf77
diff --git a/.gitignore b/.gitignore
index 5081960..2ea50a0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,4 +2,5 @@
 build/
 ethos_u_vela.egg-info/
 ethosu/*.so
-.coverage
\ No newline at end of file
+.coverage
+__pycache__