mm: for !CONFIG_PER_VMA_LOCK equate write lock assertion for vma and mmap

mm: for !CONFIG_PER_VMA_LOCK equate write lock assertion for vma and mmap

When CONFIG_PER_VMA_LOCK=n, vma_assert_write_locked() should be equivalent
to mmap_assert_write_locked().

Link: https://lkml.kernel.org/r/20230804152724.3090321-3-surenb@google.com
Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>