ACPI: tools: Fix compilation when output directory is not present

Compiling the ACPI tools when output directory parameter is specified,
but the output directory is not present, triggers the following error:

make O=/data/test/tmp/ -C tools/power/acpi/

make: Entering directory '/data/src/kernel/linux/tools/power/acpi'
  DESCEND tools/acpidbg
make[1]: Entering directory '/data/src/kernel/linux/tools/power/acpi/tools/acpidbg'
  MKDIR    include
  CP       include
  CC       tools/acpidbg/acpidbg.o
Assembler messages:
Fatal error: can't create /data/test/tmp/tools/power/acpi/tools/acpidbg/acpidbg.o: No such file or directory
make[1]: *** [../../Makefile.rules:24: /data/test/tmp/tools/power/acpi/tools/acpidbg/acpidbg.o] Error 1
make[1]: Leaving directory '/data/src/kernel/linux/tools/power/acpi/tools/acpidbg'
make: *** [Makefile:18: acpidbg] Error 2
make: Leaving directory '/data/src/kernel/linux/tools/power/acpi'

which occurs because the output directory has not been created yet.

Fix this issue by creating the output directory before compiling.

Reported-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
[ rjw: New subject, changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>