staging: greybus: audio: Uninitialized variable in gbaudio_remove_controls()

The "err" variable is not meaningful so there is no need to print it.
It's uninitialized on the first iteration through the loop.

Fixes: 510e340e

 ("staging: greybus: audio: Add helper APIs for dynamic audio modules")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Reviewed-by: Vaibhav Agarwal <vaibhav.sr@gmail.com>
Link: https://lore.kernel.org/r/20200804101601.GA392148@mwanda
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>