staging: nvec: remove managed resource from PS2 driver

This basicly reverts commit e534f3e9

 (staging:nvec: Introduce the use of
the managed version of kzalloc). Serio struct should never by managed
because it is refcounted. Doing so will lead to a double free oops on module
remove.

Signed-off-by: Marc Dietrich <marvin24@gmx.de>
Fixes: e534f3e9

 ("staging:nvec: Introduce the use of the managed version of kzalloc")
Cc: stable <stable@vger.kernel.org> # 3.15+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>