kill mm argument of vm_munmap()

it's always current->mm

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/aio.c b/fs/aio.c
index 976e33d..67a6db3 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -94,7 +94,7 @@
 
 	if (info->mmap_size) {
 		BUG_ON(ctx->mm != current->mm);
-		vm_munmap(ctx->mm, info->mmap_base, info->mmap_size);
+		vm_munmap(info->mmap_base, info->mmap_size);
 	}
 
 	if (info->ring_pages && info->ring_pages != info->internal_pages)