When per-channel tx/rx time is printed in wlan driver, the
current code checks whether service bit
wmi_service_ll_stats_per_chan_rx_tx_time is enabled in every
loop, which will result in very verbose logs printed on
some platforms where the above service bit is not indicated
by firmware.
Check whether wmi_service_ll_stats_per_chan_rx_tx_time is
enabled only once whenever wlan link radio stat event is
handled to reduce the unnecessary verbose logging.
Change-Id: I438df8ab307a793ac108503c767373a79e817919
CRs-Fixed: 2804956