rust: time: Add PartialEq/Eq/PartialOrd/Ord trait to Ktime

rust: time: Add PartialEq/Eq/PartialOrd/Ord trait to Ktime

Add PartialEq/Eq/PartialOrd/Ord trait to Ktime so two Ktime instances
can be compared to determine whether a timeout is met or not.

Use the derive implements; we directly touch C's ktime_t rather than
using the C's accessors because it is more efficient and we already do
in the existing code (Ktime::sub).

Reviewed-by: Trevor Gross <tmgross@umich.edu>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Fiona Behrens <me@kloenk.dev>
Tested-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Link: https://lore.kernel.org/r/20250423192857.199712-3-fujita.tomonori@gmail.com
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>