ASoC: Intel: atom: Take the drv->lock mutex before calling sst_send_slot_map()

sst_send_slot_map() uses sst_fill_and_send_cmd_unlocked() because in some
places it is called with the drv->lock mutex already held.

So it must always be called with the mutex locked. This commit adds missing
locking in the sst_set_be_modules() code-path.

Fixes: 24c8d141

 ("ASoC: Intel: mrfld: add DSP core controls")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200402185359.3424-1-hdegoede@redhat.com
Signed-off-by: Mark Brown <broonie@kernel.org>