buttons: Remove legacy button applications

The button applications have moved to their own project here:
https://github.com/openbmc/phosphor-buttons

Remove the legacy rstbutton and pwrbutton appications.

Change-Id: I16d0e364bd748551cf4d33244e07de79e069dedc
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
5 files changed