arch: arm64: core: Fix issue IPI for non-booted core

During Zephyr boot with SMP enabled,
while z_smp_init is not completed yet and only boot core is running,
incorrect code in broadcast_ipi API will cause following:
1. Generate IPI even if other cores are not booted.
2. Incorrect setting of sgi1r register.
3. All the affinity(1/2/3) value will be incorrect.

Signed-off-by: Chirag Kochar <chirag.kochar@intel.com>