wifi: ath11k: fix tid bitmap is 0 in peer rx mu stats

Correct parsing of reading offset for rx tid 16 bit bitmap. Incorrect
offset caused peer rx mu stats tid bitmap to always be zero. This
correction is in the software context and does not affect the
firmware interface.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.4.0.1-00356-QCAHKSWPL_SILICONZ-1

Signed-off-by: Muna Sinada <quic_msinada@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/1692827868-15667-2-git-send-email-quic_msinada@quicinc.com