ath11k: avoid while loop in ring selection of tx completion interrupt

Currently while loop is used to find the tx completion ring number and
it is not required since the tx ring mask and the group id can be combined
to directly fetch the ring number. Hence remove the while loop
and directly get the ring number from tx mask and group id.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.4.0.1-01734-QCAHKSWPL_SILICONZ-1 v2

Co-developed-by: Sriram R <srirrama@codeaurora.org>
Signed-off-by: Sriram R <srirrama@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: P Praneesh <ppranees@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1630560820-21905-11-git-send-email-ppranees@codeaurora.org