firmware: cs_dsp: Fix OOB memory read access in KUnit test

KASAN reported out of bounds access - cs_dsp_mock_bin_add_name_or_info(),
because the source string length was rounded up to the allocation size.

Cc: Simon Trimmer <simont@opensource.cirrus.com>
Cc: Charles Keepax <ckeepax@opensource.cirrus.com>
Cc: Richard Fitzgerald <rf@opensource.cirrus.com>
Cc: patches@opensource.cirrus.com
Cc: stable@vger.kernel.org
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Link: https://patch.msgid.link/20250523102102.1177151-1-perex@perex.cz


Reviewed-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>