8852BE doesn't support some TX channels, so mask them out, or it access
undefined registers.
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220927062611.30484-2-pkshih@realtek.com