wifi: rtw89: declare support bands with const

They are just default declarations and we won't modify them directly.
Instead, we actually do moification on their memdup now. So, they
should be declared with const.

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/20221020052702.33988-1-pkshih@realtek.com