Read instruction with byte_order_for_code

Read instruction with byte_order_for_code

When reading instruction, we should use byte_order_for_code instead
of byte_order.

gdb:

2016-01-13  Yao Qi  <yao.qi@linaro.org>

	* arch/arm-get-next-pcs.c (arm_get_next_pcs_raw): Use
	byte_order_for_code to read instruction.