firmware: cs_dsp: Ensure cs_dsp_load[_coeff]() returns 0 on success

Set ret = 0 on successful completion of the processing loop in
cs_dsp_load() and cs_dsp_load_coeff() to ensure that the function
returns 0 on success.

All normal firmware files will have at least one data block, and
processing this block will set ret == 0, from the result of either
regmap_raw_write() or cs_dsp_parse_coeff().

The kunit tests create a dummy firmware file that contains only the
header, without any data blocks. This gives cs_dsp a file to "load"
that will not cause any side-effects. As there aren't any data blocks,
the processing loop will not set ret == 0.

Originally there was a line after the processing loop:

    ret = regmap_async_complete(regmap);

which would set ret == 0 before the function returned.

Commit fe08b7d ("firmware: cs_dsp: Remove async regmap writes")
changed the regmap write to a normal sync write, so the call to
regmap_async_complete() wasn't necessary and was removed. It was
overlooked that the ret here wasn't only to check the result of
regmap_async_complete(), it also set the final return value of the
function.

Fixes: fe08b7d ("firmware: cs_dsp: Remove async regmap writes")
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://patch.msgid.link/20250323170529.197205-1-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/firmware/cirrus/cs_dsp.c

@@ -1631,6 +1631,7 @@ static int cs_dsp_load(struct cs_dsp *dsp, const struct firmware *firmware,
 
 	cs_dsp_debugfs_save_wmfwname(dsp, file);
 
+	ret = 0;
 out_fw:
 	cs_dsp_buf_free(&buf_list);
 
@@ -2338,6 +2339,7 @@ static int cs_dsp_load_coeff(struct cs_dsp *dsp, const struct firmware *firmware
 
 	cs_dsp_debugfs_save_binname(dsp, file);
 
+	ret = 0;
 out_fw:
 	cs_dsp_buf_free(&buf_list);