Fix meanwell app-meanwell.toml so that the output doesn't conflict wi…

…th app.toml (#1567)

If one builds all of the available app.toml then the outputs of
app/gimletlet/app{,-meanwell}.toml get written to the same path:
target/gimletlet-meanwell/dist/default/build-gimletlet-image-default.zip

This change results in app-meanwell.toml writing to:
target/gimletlet-meanwell/dist/default/build-gimletlet-meanwell-image-default.zip

app/gimletlet/app-meanwell.toml

@@ -1,4 +1,4 @@
-name = "gimletlet"
+name = "gimletlet-meanwell"
 target = "thumbv7em-none-eabihf"
 board = "gimletlet-2"
 chip = "../../chips/stm32h7"