arch: call arch_smp_init() directly, do not use SYS_INIT

Move this to a call in the init process. arch_* calls are no services
and should be called consistently during initialization.

Place it between PRE_KERNEL_1 and PRE_KERNEL_2 as some drivers
initialized in PRE_KERNEL_2 might depend on SMP being setup.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>