wifi: rtw88: use struct instead of macros to set TX desc

Remove macros that set TX descriptors. Use struct and
le32_encode_bits() with mask definitions.

Signed-off-by: Po-Hao Huang <phhuang@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/20230616125540.36877-2-pkshih@realtek.com