staging/nvec: Remove double const qualifier

The SIMPLE_DEV_PM_OPS macro already uses the const qualifier, so there's
no need to repeat it.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Marc Dietrich <marvin24@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>