ARCv2: Enable unaligned access in early ASM code

commit 252f6e8eae909bc075a1b1e3b9efb095ae4c0b56 upstream.

It is currently done in arc_init_IRQ() which might be too late
considering gcc 7.3.1 onwards (GNU 2018.03) generates unaligned
memory accesses by default

Cc: stable@vger.kernel.org #4.4+
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
[vgupta: rewrote changelog]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>