meta-romulus: Add id-button.bb

This recipe adds the function to assert/deassert identify LED Group
when the ID button is pressed:
1. Add phosphor-gpio-monitor for the ID button GPIO key;
2. Start id-button-pressed.service when the key is pressed;
3. The service starts a script to check the identify LED group state,
   and assert or de-assert it.

Tested: Assert/De-assert identify LED group by pressing the ID button
        on Romulus.

Change-Id: I782dbc15563a313418aa90bee1f48fc97a6d25fb
Signed-off-by: Lei YU <mine260309@gmail.com>
5 files changed