ARM: shmobile: Remove unused shmobile_smp_init_cpus()

Remove shmobile_smp_init_cpus() since all SMP platforms in
mach-shmobile now rely on DT for CPU core description instead
of for instance determining number of cores from the SCU.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>