ANDROID: binder: Drop lru lock in isolate callback

Drop the global lru lock in isolate callback
before calling zap_page_range which calls
cond_resched, and re-acquire the global lru
lock before returning. Also change return
code to LRU_REMOVED_RETRY.

Use mmput_async when fail to acquire mmap sem
in an atomic context.

Fix "BUG: sleeping function called from invalid context"
errors when CONFIG_DEBUG_ATOMIC_SLEEP is enabled.

Change-Id: I45dbada421b715abed9a66d03d30ae2285671ca1
Fixes: f2517eb76f1f2 ("android: binder: Add global lru shrinker to binder")
Reported-by: Kyle Yan <kyan@codeaurora.org>
Acked-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Sherry Yang <sherryy@android.com>
Patch-mainline: lkml @ 09/08/17, 18:39
Signed-off-by: Kyle Yan <kyan@codeaurora.org>