ath10k: Fill rx duration for each peer in fw_stats for WCN3990

Currently, rx_duration for each peer is not getting populated in
fw_stats debugfs entry for WCN3990.

WCN3990 firmware sends rx duration for each peer as part of
peer_extd_stats in WMI_UPDATE_STATS_EVENT. To enable peer_extd_stats,
firmware expects host to send fw_stats_req_mask with flag
WMI_TLV_PEER_STATS_EXTD set in WMI_REQUEST_STATS_CMD.

Send fw_stats_req_mask with flag WMI_TLV_PEER_STATS_EXTD set in
WMI_REQUEST_STATS_CMD and parse the peer_extd_stats in
WMI_UPDATE_STATS_EVENT to populate the rx_duration of each peer
in fw_stats debugfs entry.

Currently the driver handles 32-bit rx_duration, but the rx_duration
for WCN3990 can be upto 63 bit. The firmware sends rx_duration split
into two 32-bit fields, with the upper 32-bits being valid only if its
MSB is set. This change handles the 63-bit rx_duration obtained from
WCN3990 and maintain the backward compatibility.

To get the rx_duration of each connected peer :
cat /sys/kernel/debug/ieee80211/phyX/ath10k/fw_stats

Tested HW: WCN3990
Tested FW: WLAN.HL.3.1-00784-QCAHLSWMTPLZ-1

Signed-off-by: Surabhi Vishnoi <svishnoi@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>