libbladeRF: Cleaned up si5338 output levels

The debug level is intended for higher level operation and information
pertaining to why error values are returned.

Therefore, low-level messages have been moved to the verbose log level,
and error messages have been moved to debug.

The error log level is intended for fatal conditions that will likely
lead to a crash, rather than cleanly return an error code.
libbladeRF: Cleaned up log lines in si5338.c

Aesthetic change only. It is preferred that lines be <= 80 characters.