ARM: extract_arm_insn function need to read instrs correctly in be8 case

ARM: extract_arm_insn function need to read instrs correctly in be8 case

extract_arm_insn function needs to read instructions in
gdbarch_byte_order_for_code byte order, because in case armv7b,
even data is big endian, instructions are still little endian.
Currently function uses gdbarch_byte_order which would be
big endian in armv7b case.

Because of this issue pretty much all gdb.reverse/ tests are
failing with 'Process record does not support instruction' message.

Fix is to change gdbarch_byte_order to gdbarch_byte_order_for_code,
when passed to extract_unsigned_integer that reads instruction.

gdb/ChangeLog:

2014-11-02  Victor Kamensky  <victor.kamensky@linaro.org>

	* arm-tdep.c (extract_arm_insn): Use
	gdbarch_byte_order_for_code to read arm instruction.