kernel: sys.c: fix compile, we don't have that function without NVIDIAS hotplug manager

Signed-off-by: Dennis Rassmann <showp1984@gmail.com>

Conflicts:

	kernel/sys.c
mach-tegra: tegra_mpdecision: increase hysteresis limit and add comment

Signed-off-by: Dennis Rassmann <showp1984@gmail.com>