ARM: tegra: fix compile error when disable CPU_IDLE

The "sleep.S" file has many functions that be shared by different module
currently. Not just for CPU idle driver. Make it build as default now.

Reported-by: Rhyland Klein <rklein@nvidia.com>
Signed-off-by: Joseph Lo <josephl@nvidia.com>
[swarren: add sleep.o to separate line so each line only contains 1 file]
Signed-off-by: Stephen Warren <swarren@nvidia.com>