arm-dis: Include opcode hex when doing disassembly

Enhance the ARM disassembler used for debugging so that it includes
the hex dump of the opcode as well as the symbolic disassembly.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>