ANDROID: mm: fix locking in do_madvise() when CONFIG_MEMORY_FAILURE=y

Backport of 4cc39f91 leaves madvise_lock
lockedin one of the paths with CONFIG_MEMORY_FAILURE=y. Fix by dropping
the lock before returning.

Fixes: 87cddfad ("BACKPORT: mm/madvise: split out mmap locking operations for madvise()")
Bug: 425827225
Reported-by: yipeng xiang <yipengxiang@honor.corp-partner.google.com>
Change-Id: I41899e3a95e62be5ec8638a9ea8bc3c7e3da529f
Signed-off-by: Suren Baghdasaryan <surenb@google.com>