crypto: omap-aes - use runtime_pm autosuspend for clock handling

Calling runtime PM API at the cra_init/exit is bad for power management
purposes, as the lifetime for a CRA can be very long. Instead, use
pm_runtime autosuspend approach for handling the device clocks. Clocks
are enabled when they are actually required, and autosuspend disables
these if they have not been used for a sufficiently long time period.
By default, the timeout value is 1 second.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>