FROMGIT: ASoC: sprd: Allow the MCDT driver to build into modules

Change the config to 'tristate' for MCDT driver to allow it to build into
modules, as well as changing to use IS_ENABLED() to validate if need supply
dummy functions when building the MCDT driver as a module.

bug: 151273001
Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Link: https://lore.kernel.org/r/9306f2b99641136653ae4fe6cf9e859b7f698f77.1583387748.git.baolin.wang7@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>
(cherry picked from commit fd357ec595d36676c239d8d16706a270a961ac32
https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-next)