rtlwifi: Add Support VHT to spec_ver

We are going to add 8822be, which is a VHT 2x2 wifi chip, so add VHT flag
to replace enumeration of chips.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>