wifi: rtw89: fix potential leak in rtw89_append_probe_req_ie()

Do `kfree_skb(new)` before `goto out` to prevent potential leak.

Fixes: 89590777 ("rtw89: 8852a: add ieee80211_ops::hw_scan")
Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230103141054.17372-1-pkshih@realtek.com