ASoC: SDCA: Fix return value in sdca_regmap_mbq_size()

The MBQ size function returns an integer representing the size of a
Control. Currently if the Control is not found the function will return
false which makes little sense. Correct this typo to return -EINVAL.

Fixes: e3f7caf7 ("ASoC: SDCA: Add generic regmap SDCA helpers")
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Message-ID: <20250820163717.1095846-2-ckeepax@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>