ath11k: Change masking and shifting in htt stats

ath11k: Change masking and shifting in htt stats

In debugfs_htt_stats.c, masking and shifting is done to get
stats values. Instead use GENMASK and FIELD_GET to improve
code readability and maintenance.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.5.0.1-01105-QCAHKSWPL_SILICONZ-1

Signed-off-by: Seevalamuthu Mariappan <seevalam@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210913223148.208026-5-jouni@codeaurora.org