ASoC: cs35l56: Use SoundWire address as alternate firmware suffix on L56 B0

Use the SoundWire link number and device unique ID as the firmware file
qualifier suffix on CS35L56 B0 if .bin files are not found with the older
suffix. Some changes in wm_adsp needed to support this have been included
in this patch because they are trivial.

The allows future products with CS35L56 B0 silicon to use the same firmware
file naming as CS35L57 and cs35L63, while retaining backward compatibility
for firmware that has already been published with the old naming scheme.

The old suffix is searched first, partly because there are already many
files using that naming scheme, but also because they are a smaller subset
of all the possible fallback name options offered by wm_adsp so we know
that it will either find the qualified files or fail. All the firmware
files already published have the wmfw qualified with only the ACPI SSID and
the bin files qualified with both SSID and the suffix.

Originally, the firmware file names indicated which amplifier instance they
were for by appending the ALSA prefix string. This is the standard ASoC way
of distinguishing different instances of the same device. However, on
SoundWire systems the SoundWire physical unique address is available as a
unique identifier for each amp, and this address is hardwired by the
address pin on the amp.

The firmware files are specific for each physical amp so they must be
applied to that amp. Using the ALSA prefix for the filename qualifier means
that to name a firmware file it must be determined what prefix string the
machine driver will assign to each device and then use that to name the
firmware file correctly. This is straightforward in traditional ASoC
systems where the machine driver is specific to a particular piece of
hardware. But on SoundWire the machine driver is generic and can handle a
very wide range of hardware. It is more difficult to determine exactly what
the prefix will be on any particular production device, and more prone to
mistakes. Also, when the machine driver switches to generating this
automatically from SDCA properties in ACPI, there is an additional layer of
complexity in determining the mapping. This uncertainty is unnecessary
because the firmware is built for a specific amp. with known address, so we
can use that directly instead of introducing a redundant intermediate
alias. This ensures the firmware is applied to the amp it was intended for.

There are already many published firmware for CS35L56 B0 silicon so this
first looks for the original name suffix, to keep backward compatibility.
If this doesn't find .bin files it will switch to using the new name suffix
so that future products using CS35L56 B0 can start to use the new suffix.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://patch.msgid.link/20250612121428.1667-3-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

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