ASoC: sigmadsp: Refuse to load firmware files with a non-supported version

Make sure to check the version field of the firmware header to make sure to
not accidentally try to parse a firmware file with a different layout.
Trying to do so can result in loading invalid firmware code to the device.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org