rust: miscdevice: access file in fops

This allows fops to access information about the underlying struct file
for the miscdevice. For example, the Binder driver needs to inspect the
O_NONBLOCK flag inside the fops->ioctl() hook.

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Lee Jones <lee@kernel.org>
Tested-by: Lee Jones <lee@kernel.org>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20241210-miscdevice-file-param-v3-1-b2a79b666dc5@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>