misc: mic: remove unused label 'done'

The label 'done' in function vop_ioctl is not used, so remove it. Fixes
build warning:

drivers/misc/mic/vop/vop_vringh.c:1001:1: warning: label 'done' defined but
not used [-Wunused-label]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>