[doc] Set up PLL when getting started with CW310

If the --set-pll-defaults argument is missing, the new user will have
no clock.

Signed-off-by: Alexander Williams <awill@google.com>
diff --git a/doc/ug/getting_started_fpga.md b/doc/ug/getting_started_fpga.md
index 1c751d4..b883ec6 100644
--- a/doc/ug/getting_started_fpga.md
+++ b/doc/ug/getting_started_fpga.md
@@ -162,7 +162,7 @@
 1. Run the loading tool.
    ```console
    $ cd ${REPO_TOP}
-   $ ./util/fpga/cw310_loader.py --firmware build-bin/sw/device/examples/hello_world/hello_world_fpga_cw310.bin
+   $ ./util/fpga/cw310_loader.py --firmware build-bin/sw/device/examples/hello_world/hello_world_fpga_cw310.bin --set-pll-defaults
    ```
 
    This should report how the binary is split into frames: