log: Avoid including function names by default

log: Avoid including function names by default

Unless function names are requested, the logging system should not
compile these into the code. Adjust the macros to handle this.

This means that turning on function names at runtime won't work unless
CONFIG_LOGF_FUNC is enabled. We could perhaps split this into a
separate option if that is a problem.

Enable CONFIG_LOGF_FUNC logging for sandbox since the tests expect the
function names to be included. Fix up the pinmux test which checks a
logging statement.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>