[riscv64] Add base power manager config to image

This enables the power_manager component to start; without this, it
silently exits with an error, causing the root job to also exit and the
system to halt.

Bug: 129166
Change-Id: Ia024dc0357a1d3e149b2149e79a6b7d179784930
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/871237
Reviewed-by: David Dorwin <[email protected]>
Fuchsia-Auto-Submit: Alex Konradi <[email protected]>
Commit-Queue: Auto-Submit <[email protected]>
Reviewed-by: Aaron Wood <[email protected]>

Author: akonradi

boards/riscv64.gni

@@ -22,6 +22,9 @@ platform_enable_user_pci = true
 board_bootfs_labels += [
   "//src/devices/bus/drivers/pci:bus-pci",
   "//src/devices/board/drivers/qemu-riscv64",
+
+  # Configs
+  "//src/power/power-manager:base_config",
 ]
 board_bootfs_labels += _imports.virtio_drivers