meta-fii: meta-kudo: Use phosphor-buttons package

The method to monitor the power and reset buttons through the
ampere_power_util.sh with phosphor-gpio-monitor was a temporary
solution. It was a temporary workaround until there is support for
Nuvoton GPIO in phosphor-buttons.

Signed-off-by: Charles Boyer <Charles.Boyer@fii-usa.com>
Change-Id: I34541c0f56887962ad780b811eae44f1d851059d