firmware: cs_dsp: Support DSPs that don't require firmware download

When a DSP can self-boot from ROM it is not necessary to download
firmware during the powering up sequence.

A DSP that required firmware download would fail in a previous
configuration step if firmware was not available.
Signed-off-by: Simon Trimmer <simont@opensource.cirrus.com>
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230320112245.115720-4-rf@opensource.cirrus.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/firmware/cirrus/cs_dsp.c

@@ -1301,6 +1301,9 @@ static int cs_dsp_load(struct cs_dsp *dsp, const struct firmware *firmware,
 	int regions = 0;
 	int ret, offset, type;
 
+	if (!firmware)
+		return 0;
+
 	ret = -EINVAL;
 
 	pos = sizeof(*header) + sizeof(*adsp1_sizes) + sizeof(*footer);