arm64: enable processor debug state for secondary cpus

arm64: enable processor debug state for secondary cpus

processor debug state PSTATE.D is unmasked in smp call
clear_os_lock for secondary cpus. So debug state is still
masked in normal kernel context.  With this patch, unmask
debug state on secondary boot for the cpus in normal kernel
context. Now kgdb tests passed with multicore.

Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit d8ed442a009ecfe155b57d58f231db3d6084633d)
Signed-off-by: Mark Brown <broonie@linaro.org>
Conflicts:
	arch/arm64/kernel/smp.c