fw_update: use different package names for each board

Update this reference design to work with Cohorts by assigning package
names to each type of unique hardware.

Signed-off-by: Mike Szczys <mike@golioth.io>

Author: szczys

README.md

@@ -189,7 +189,10 @@ version number than what is currently running on the device.
 2. Upload the `build/app/zephyr/zephyr.signed.bin` file as a Package for
    your Golioth project.
 
-   - Use `main` as the package name.
+   - Use either `nrf9160dk` or `aludel_elixir` as the package name,
+     depending on which board the update file was built for. (These
+     package names were configured in this repository's board `.conf`
+     files.) Use `main` as the package name.
    - Use the same version number from step 1.
 
 3. Create a Cohort and add your device to it.

boards/aludel_elixir_ns.conf

@@ -6,3 +6,6 @@ CONFIG_ALUDEL_BATTERY_MONITOR=y
 
 # Turn on regulator to power click headers
 CONFIG_REGULATOR=y
+
+# Use a unique package name to use with Packages/Cohorts/Deployments
+CONFIG_GOLIOTH_FW_UPDATE_PACKAGE_NAME="aludel_elixir"

boards/nrf9160dk_nrf9160_ns.conf

@@ -0,0 +1,2 @@
+# Use a unique package name to use with Packages/Cohorts/Deployments
+CONFIG_GOLIOTH_FW_UPDATE_PACKAGE_NAME="nrf9160dk"