wifi: rtw89: 8852c: make table of RU mask constant

This table must be constant, so change it as expectation.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20221020052702.33988-2-pkshih@realtek.com