ASoC: sigmadsp: uninitialized variable in sigmadsp_activate_ctrl()

The "changed" variable should be set to false at the start.

Fixes: a35daac7 ('ASoC: sigmadsp: Add support for fw v2')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>