ASoC: Intel: atom: Fix uninitialized variable compiler warning

GCC 10 gives a "variable might be used uninitialized" warning for the
block variable in sst_prepare_and_post_msg().

This is a false-positive warning, but lets fix it anyways.
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/20200402185359.3424-3-hdegoede@redhat.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/atom/sst/sst_pvt.c

@@ -223,9 +223,9 @@ int sst_prepare_and_post_msg(struct intel_sst_drv *sst,
 		size_t mbox_data_len, const void *mbox_data, void **data,
 		bool large, bool fill_dsp, bool sync, bool response)
 {
+	struct sst_block *block = NULL;
 	struct ipc_post *msg = NULL;
 	struct ipc_dsp_hdr dsp_hdr;
-	struct sst_block *block;
 	int ret = 0, pvt_id;
 
 	pvt_id = sst_assign_pvt_id(sst);