drm/tyr: suppress unread field warnings

drm/tyr: suppress unread field warnings

Currently the rust compiler warns that certain fields in the TyrDriver are
'never read'. The fields are needed, but they are not read directly, they
are only written into an 'impl PinInit' that is returned by probe.

When warnings are compiled as errors, these warnings prevent Tyr from
building.

Suppress the warnings by adding underscores to the problematic variables.
This allows Tyr to build again.

Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260123175235.209092-1-deborah.brouwer@collabora.com
Signed-off-by: Alice Ryhl <aliceryhl@google.com>