wifi: rtw89: refine element naming used by queue empty check

In queue empty check, one group contains 32 queues. And, the two elements,
wde_qempty_acq_num and wde_qempty_mgq_sel, are number of group and select
of group. To avoid confusing them with queue number and queue selection,
we refine their naming.

(don't change logic at all)

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/20231124071703.132549-5-pkshih@realtek.com