xen/arm: Remove __initdata and __init to enable CPU hotplug

xen/arm: Remove __initdata and __init to enable CPU hotplug

CPU up flow is currently used during the initial boot to start secondary
CPUs. However, the same flow should be used for CPU hotplug, e.g. when
hotplugging secondary CPUs within the resume procedure (resume from the
suspend to RAM). Therefore, prefixes __initdata and __init had to be removed
from few data structures and functions that are used within the cpu up flow.

Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
Acked-by: Julien Grall <julien.grall@arm.com>