ARM: tegra: Change tegra_set_cpu_in_lp2() type to void

The Tegra30 CPUIDLE driver has intention to check whether primary CPU was
the last CPU that entered LP2 (CC6) idle-state, but that functionality
never got utilized because driver never supported the CC6 state for the
case where any secondary CPU is online. The new cpuidle driver will
properly support CC6 on Tegra30, including the case where secondary CPUs
are online, and that knowledge about what CPUs entered into CC6 won't be
needed at all because new driver will use different approach by making use
of the coupled idle-state and explicitly parking secondary CPUs before
entering into CC6. Thus this patch is just a minor cleanup change.

Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Tested-by: Peter Geis <pgwipeout@gmail.com>
Tested-by: Jasper Korten <jja2000@gmail.com>
Tested-by: David Heidelberg <david@ixit.cz>
Tested-by: Nicolas Chauvet <kwizart@gmail.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>