wifi: rtw89: pci: concentrate control function of TX DMA channel

Different chips use different register and mask for
tx dma channels, so concentrate them.

Signed-off-by: Chin-Yen Lee <timlee@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/20220912071706.13619-4-pkshih@realtek.com