staging: nvec: make keyboard init synchronous

Currently, we are constantly sending commands to the EC without waiting for them to be
executed. This can lead to confusion, especially if we initialize several different devices
one after the other.
To avoid this, we are switching from asynchronous to synchronous command transmission.

Signed-off-by: Marc Dietrich <marvin24@gmx.de>
Link: https://lore.kernel.org/r/20240406123123.37148-3-marvin24@gmx.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>