ARM: tegra: rename the file of "sleep-tXX" to "sleep-tegraXX"

For the naming consistency under the mach-tegra, we re-name the file of
"sleep-tXX" to "sleep-tegraXX" (e.g., sleep-t30 to sleep-tegra30).

Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>