tools/power/x86/intel-speed-select: Add .gitignore file

Add a .gitignore file for build include/ and final binary.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: David Arcari <darcari@redhat.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>