Change the acq load to explict acq fence for #113

[CXWorks]

As discussed in #113 , we want to change the load acq to explict fence acq to guarantee the memory fence.
This behavior also matches to the std in Rust.

For details, please check:

1. https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4455.html
2. Use a load rather than a fence when dropping the contents of an Arc. rust-lang/rust#41714