target/avr: Add support for disassembling via option '-d in_asm'

target/avr: Add support for disassembling via option '-d in_asm'

Provide function disassembles executed instruction when '-d in_asm' is
provided.

Example:

$ qemu-system-avr -bios free-rtos/Demo/AVR_ATMega2560_GCC/demo.elf -d in_asm
    ...
    IN:
    0x0000014a:  CALL      0x3808

    IN: main
    0x00003808:  CALL      0x4b4

    IN: vParTestInitialise
    0x000004b4:  LDI       r24, 255
    0x000004b6:  STS       r24, 0
    0x000004b8:  MULS      r16, r20
    0x000004ba:  OUT       $1, r24
    0x000004bc:  LDS       r24, 0
    0x000004be:  MULS      r16, r20
    0x000004c0:  OUT       $2, r24
    0x000004c2:  RET
    ...

Suggested-by: Richard Henderson <[email protected]>
Suggested-by: Philippe Mathieu-Daudé <[email protected]>
Suggested-by: Aleksandar Markovic <[email protected]>
Signed-off-by: Michael Rolnik <[email protected]>
[rth: Fix spacing and const mnemonic arrays]
Signed-off-by: Richard Henderson <[email protected]>
Signed-off-by: Aleksandar Markovic <[email protected]>
Tested-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Signed-off-by: Thomas Huth <[email protected]>
Message-Id: <20200705140315[email protected]>
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>