staging: nvec: Include missing headers

Those headers were apparently included by other headers
previously, but are not anymore.

Signed-off-by: Julian Andres Klode <jak@jak-linux.org>
Acked-by: Marc Dietrich <marvin24@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --cc drivers/staging/nvec/nvec.h
Simple merge

diff --cc drivers/staging/nvec/nvec_kbd.c
Simple merge

diff --cc drivers/staging/nvec/nvec_ps2.c
Simple merge