media: solo6x10: fix missing snd_card_free in error handling case

Fix to goto snd_error in error handling case when fails
to do snd_ctl_add, as done elsewhere in this function.

Fixes: 28cae868 ("[media] solo6x10: move out of staging into drivers/media/pci.")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>