Floss: log error on enable_offload only when it is an error

Currently, for all boards that do not support SCO-offload, an error log
is printed even when the instruction is not to enable it.

In this CL, we print the log only when it is not supported but asked to
be enabled.

Bug: 255707592
Tag: #floss
Test: Build and verify
Change-Id: I32d712d849930be2979da98f62e0e5442c475ada