ACPICA: Debugger: Cleanup interface to the AML disassembler

If the disassembler is configured out (such as when the debugger
is part of a kernel), these debugger commands are disabled:
    List
    Disassemble
Further, the Debug (single-step) command is simplified because
each line of code cannot be disassembled.

Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Erik Schmauss <erik.schmauss@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>