Revert "trusty: add warn_unused_result for mmap() & munmap()" am: c7be62da94 am: ae9db4ced1

Original change: https://android-review.googlesource.com/c/trusty/external/musl/+/3262071

Change-Id: Ia6e238bd03b5013089146dec5c5701ec46e9c29b
Signed-off-by: Automerger Merge Worker <[email protected]>