rust: drm: remove pin annotations from drm::Device

rust: drm: remove pin annotations from drm::Device

The #[pin_data] and #[pin] annotations are not necessary for
drm::Device, since we don't use any pin-init macros, but only
__pinned_init() on the impl PinInit<T::Data, Error> argument of
drm::Device::new().

Fixes: 1e4b8896c0f3 ("rust: drm: add device abstraction")
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://lore.kernel.org/r/20250731154919.4132-4-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>