arm64: Unmask asynchronous aborts when in kernel mode

The asynchronous aborts are generally fatal for the kernel but they can
be masked via the pstate A bit. If a system error happens while in
kernel mode, it won't be visible until returning to user space. This
patch enables this kind of abort early to help identifying the cause.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --cc arch/arm64/include/asm/irqflags.h
Simple merge

diff --cc arch/arm64/kernel/setup.c
Simple merge

diff --cc arch/arm64/kernel/smp.c
Simple merge