meta-facebook: catalina: obmc-phosphor-buttons: add gpio_def.json

Debug card feature needs `HostSelector` object to identify which host is
selected. Add HOST_SELECTOR definition for phosphor-button to export
`/xyz/openbmc_project/Chassis/Buttons/HostSelector` object.

Test results:
```
root@bmc:~# busctl introspect xyz.openbmc_project.Chassis.Buttons /xyz/openbmc_project/Chassis/Buttons/HostSelector
NAME                                             TYPE      SIGNATURE RESULT/VALUE FLAGS
org.freedesktop.DBus.Introspectable              interface -         -            -
.Introspect                                      method    -         s            -
org.freedesktop.DBus.Peer                        interface -         -            -
.GetMachineId                                    method    -         s            -
.Ping                                            method    -         -            -
org.freedesktop.DBus.Properties                  interface -         -            -
.Get                                             method    ss        v            -
.GetAll                                          method    s         a{sv}        -
.Set                                             method    ssv       -            -
.PropertiesChanged                               signal    sa{sv}as  -            -
xyz.openbmc_project.Chassis.Buttons.HostSelector interface -         -            -
.MaxPosition                                     property  u         1            emits-change
.Position                                        property  u         0            emits-change writable
```

Change-Id: Ic0259d35740bee0f12bcd401752ed9b0d9ac1129
Signed-off-by: Potin Lai <potin.lai@quantatw.com>
diff --git a/meta-facebook/meta-catalina/recipes-phosphor/chassis/obmc-phosphor-buttons/gpio_defs.json b/meta-facebook/meta-catalina/recipes-phosphor/chassis/obmc-phosphor-buttons/gpio_defs.json
new file mode 100644
index 0000000..d66c175
--- /dev/null
+++ b/meta-facebook/meta-catalina/recipes-phosphor/chassis/obmc-phosphor-buttons/gpio_defs.json
@@ -0,0 +1,10 @@
+{
+        "gpio_definitions": [
+            {
+                "name": "HOST_SELECTOR",
+                "group_gpio_config" : [],
+                "max_position" : 1,
+                "host_selector_map" : {}
+            }
+        ]
+}
diff --git a/meta-facebook/meta-catalina/recipes-phosphor/chassis/obmc-phosphor-buttons_%.bbappend b/meta-facebook/meta-catalina/recipes-phosphor/chassis/obmc-phosphor-buttons_%.bbappend
new file mode 100644
index 0000000..91e994e
--- /dev/null
+++ b/meta-facebook/meta-catalina/recipes-phosphor/chassis/obmc-phosphor-buttons_%.bbappend
@@ -0,0 +1,10 @@
+FILESEXTRAPATHS:append := "${THISDIR}/${PN}:"
+
+SRC_URI += "file://gpio_defs.json"
+
+do_install:append() {
+        install -d ${D}${sysconfdir}/default/obmc/gpio/
+        install -m 0644 ${WORKDIR}/gpio_defs.json ${D}/${sysconfdir}/default/obmc/gpio/
+}
+
+FILES:${PN}-signals:append = " ${sysconfdir}/default/obmc/gpio/gpio_defs.json"