render_thread: Attempt to set affinity to a random fast core

render_thread: Attempt to set affinity to a random fast core

We've been pinning the render thread for every EFL process to core 0.
This is a bit silly in the first place, but some big.LITTLE arm systems,
such as exynos 5422, have the LITTLE cores first.

On those systems we put all the render threads on a slow core.

This attempts to fix that by using a random core from the pool of fast
cores.

If we can't determine which cores are fast (ie: we're not on a
linux kernel with cpufreq enabled) then we'll continue doing what we've
always done - pin to core 0.