ASoC: cs35l56: Don't overwrite a patched firmware

ASoC: cs35l56: Don't overwrite a patched firmware

Only attempt to download wmfw/bin files to a non-secured part if
it reports FIRMWARE_MISSING. If FIRMWARE_MISSING is false the
firmware has already been patched and overwriting the patch could
corrupt the running firmware.

For a secured part the wmfw/bin can be downloaded even if
FIRMWARE_MISSING is false, because they will only patch tunings.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230815124826.5447-3-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>