ASoC: SOF: ipc4-topology: Fix an unsigned comparison which can never be negative

The return value from the call to sof_ipc4_get_valid_bits() is int.
However, the return value is being assigned to an unsigned
int variable 'out_ref_valid_bits', so making it an int.

Eliminate the following warning:
./sound/soc/sof/ipc4-topology.c:1537:6-24: WARNING: Unsigned expression compared with zero: out_ref_valid_bits < 0
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=4985Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20230516081116.71370-1-yang.lee@linux.alibaba.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/ipc4-topology.c

@@ -1386,8 +1386,8 @@ sof_ipc4_prepare_copier_module(struct snd_sof_widget *swidget,
 	void **ipc_config_data;
 	int *ipc_config_size;
 	u32 **data;
-	int ipc_size, ret;
-	u32 out_ref_rate, out_ref_channels, out_ref_valid_bits;
+	int ipc_size, ret, out_ref_valid_bits;
+	u32 out_ref_rate, out_ref_channels;
 	u32 deep_buffer_dma_ms = 0;
 	int output_fmt_index;