eina_thread: Don't ensure affinity core is lower than number of cpus

eina_thread: Don't ensure affinity core is lower than number of cpus

CPUs can be turned off after boot leading to a sparse mapping of core ids.

For example, if I turn off the first four cores on an exynos 5422 (these
are the low speed cores) then the high speed cores are still numbered 4-7
but there are only 4 cores present.

In that situation using affinity_core % num_cpus will prevent ever being
able to set affinity at all.

Just remove the pointless check and let the user set whatever core id they
want.