Merge #232

232: update tock submodule to fix CI r=jrvanwhy a=hudson-ayers

This updates the Tock submodule to current master to bring in this fix: https://github.com/tock/tock/commit/b58812b63f1682d008ceab881121b27a301f3af8 which updated the OpenTitan boot ROM download location.

Co-authored-by: Hudson Ayers <hayers@stanford.edu>
diff --git a/tock b/tock
index 6e38588..6260afa 160000
--- a/tock
+++ b/tock
@@ -1 +1 @@
-Subproject commit 6e38588c73dbd78d274c00ae7fb7789b78cf6856
+Subproject commit 6260afac204ae9f469abe9e2573cb51d3b124624