sony-laptop: Add support for extended hotkeys

Recent Sony SR-series machines have an additional set of buttons accessed
via the 0x127 method rather than the 0x100 method. Add support for these.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Len Brown <len.brown@intel.com>