MAC Address as Serial Number in Embedded Systems
Yes it is ok, why wouldn't it be? Example is a cc2640 BLE chip from TI - here you can read the BLE MAC assigned by TI either by JTAG and Flash Programmer 2 



or via the GAP protocol in software

GAPRole_GetParameter(GAPROLE_BD_ADDR, ownAddress);


What security risk would it present ?
This is the information I get when I look it up.


  Result for: 54-6C-0E-A0-4A-D5
  
  Address Prefix    54:6C:0E
  
  Vendor / Company  Texas Instruments
  
  Start Address 546C0E000000
  
  End Address   546C0EFFFFFF
  
  Company Address   12500 Ti Blvd Dallas Tx 75243 Us