MTD M2PX: If we READ while a write/erase is pending, the command is ignored...

MTD M2PX: If we READ while a write/erase is pending, the command is ignored and the write/erase continues. If we dont catch this situation we will return garbage to the user because the flash will not execute the command.  So READ MUST wait for write completion, and before that, the bus must be locked since it's a precondition to calling waitwritecomplete().