arm64: create macro to park cpu in an infinite loop

A macro early_park_cpu is added to park the faulted cpu in an infinite
loop. Currently, this macro is substituted in two instances and may be
reused in future.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>