ASoC: wm_adsp: Handle optional legacy support

The tracing capabilities for the speaker protection fw enabled via
commit c55b3e46 ("ASoC: wm_adsp: Add trace caps to speaker
protection FW") are not be available on all platforms, such as the
Valve's Steam Deck which is based on the Halo Core DSP.

As a consequence, whenever the firmware is loaded, a rather misleading
'Failed to parse legacy: -19' error message is written to the kernel
ring buffer:

[  288.977412] steamdeck kernel: cs35l41 spi-VLV1776:01: DSP1: Firmware version: 3
[  288.978002] steamdeck kernel: cs35l41 spi-VLV1776:01: DSP1: cs35l41-dsp1-spk-prot.wmfw: Fri 02 Apr 2021 21:03:50 W. Europe Daylight Time
[  289.094065] steamdeck kernel: cs35l41 spi-VLV1776:01: DSP1: Firmware: 400a4 vendor: 0x2 v0.33.0, 2 algorithms
[  289.095073] steamdeck kernel: cs35l41 spi-VLV1776:01: DSP1: 0: ID cd v29.53.0 XM@94 YM@e
[  289.095665] steamdeck kernel: cs35l41 spi-VLV1776:01: DSP1: 1: ID f20b v0.0.1 XM@170 YM@0
[  289.096275] steamdeck kernel: cs35l41 spi-VLV1776:01: DSP1: Protection: C:\Users\ocanavan\Desktop\cirrusTune_july2021.bin
[  291.172383] steamdeck kernel: cs35l41 spi-VLV1776:01: DSP1: Failed to parse legacy: -19

Update wm_adsp_buffer_init() to print a more descriptive info message
when wm_adsp_buffer_parse_legacy() returns -ENODEV.

Fixes: c55b3e46

 ("ASoC: wm_adsp: Add trace caps to speaker protection FW")
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20220825220530.1205141-1-cristian.ciocaltea@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>