nfc: fix error handling of nfc_proto_register()

When nfc proto id is using, nfc_proto_register() return -EBUSY error
code, but forgot to unregister proto. Fix it by adding proto_unregister()
in the error handling case.

Fixes: c7fe3b52

 ("NFC: add NFC socket family")
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20211013034932.2833737-1-william.xuanziyang@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>