FROMLIST: rust: miscdevice: add mmap support

Add the ability to write a file_operations->mmap hook in Rust when using
the miscdevice abstraction. The `vma` argument to the `mmap` hook uses
the `VmAreaNew` type from the previous commit; this type provides the
correct set of operations for a file_operations->mmap hook.

Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> (for mm bits)
Change-Id: I00a0769625bd9e6cbb2dc9613cda8ae371a3ac3b
Signed-off-by: Alice Ryhl <aliceryhl@google.com>

Bug: 370906207
Link: https://lore.kernel.org/all/20250115-vma-v12-7-375099ae017a@google.com/


Change-Id: I5f4441b60673fdc08190eaf566099dcb88905bb9
Signed-off-by: Alice Ryhl <aliceryhl@google.com>