ASoC: Intel: sst: Simplify is_byt_cr()

is_byt_cr() and its usage can be simplified by returning the bool
directly, instead of through a pointer. This works because the
return value is just treated as bytcr = false and is not used
otherwise.

This patch also removes the extra check of
IS_ENABLED(CONFIG_IOSF_MBI) in favor of checking
iosf_mbi_available() directly. The header already takes care
of returning false if the config option is not enabled.

No functional change.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>