add message on startup to indicate GM is locked to ext reference
Currently if a GrandMaster switch times-out when locking to an external
reference, users can see the following message:
/wr/bin/wrsw_hal: Error: Can't lock the PLL. If running in the GrandMaster mode, are you sure the 1-PPS and 10 MHz reference clock signals are properly connected?, retrying...
However, if it succeeds afterwards, there is no message saying that WRS is locked. This can be misleading for users and should be fixed.