ARM: tegra: Use clk_m CPU on Tegra124 LP1 resume

Configure the clock controller to set an alternate clock for the CPU
when it receives an IRQ during LP1 (system suspend). Specifically, use
clk_m (the crystal) rather than clk_s (a 32KHz clock). Such an IRQ will
be the LP1 wake event. This reduces the amount of time taken to resume
from LP1.

NVIDIA's downstream kernel executes this code on both Tegra30 and
Tegra124, so it appears OK to make this change unconditionally.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>