littlefs: Set specific hash for littlefs-fuse testing

Author: geky

.travis.yml

@@ -127,6 +127,7 @@ matrix:
       before_script:
         # Setup and patch littlefs-fuse
         - git clone https://github.com/geky/littlefs-fuse littlefs_fuse
+        - git -C littlefs_fuse checkout 3f1ed6e37799e49e3710830dc6abb926d5503cf2
         - echo '*' > littlefs_fuse/.mbedignore
         - rm -rf littlefs_fuse/littlefs/*
         - cp -r $(git ls-tree --name-only HEAD $LITTLEFS/littlefs/) littlefs_fuse/littlefs