Input: cros_ec_keyb - do not allocate keyboard state separately

Now that we know the upper bound for the number of columns, and know
that it is pretty small, there is no point in allocating it separately.
We are wasting more memory tracking the allocations.

Embed valid_keys and old_kb_state directly into cros_ec_keyb structure.

Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://patch.msgid.link/20260222003717.471977-6-dmitry.torokhov@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>