If there is a failure during copy_from_user or user-provided data
buffer is invalid, rtw_debugfs_set_* should return negative
error code instead of a positive value count.

Fix this bug by returning correct error code.
Signed-off-by: Zhang Shurong <zhang_shurong@foxmail.com>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/tencent_53140CC2A3468101955F02EB66AA96780B05@qq.com