cpuidle: lpm-levels: Set suspend and s2idle ops later during probe

There is a possibility of failing probe after setting suspend and
s2idle ops. Register suspend ops later during probe after which
there is no failure.

While at this, also add missing dma_free_coherent call.

Change-Id: I824f5d433623a4d7309875a61c68778f74d139f7
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>