wifi: ath10k: snoc: enable threaded napi on WCN3990

NAPI poll can be done in threaded context along with soft irq
context. Threaded context can be scheduled efficiently, thus
creating less of bottleneck during Rx processing. This patch is
to enable threaded NAPI on ath10k driver.

Based on testing, it was observed that on WCN3990, the CPU0 reaches
100% utilization when napi runs in softirq context. At the same
time the other CPUs are at low consumption percentage. This
does not allow device to reach its maximum throughput potential.
After enabling threaded napi, CPU load is balanced across all CPUs
and following improvments were observed:
- UDP_RX increase by ~22-25%
- TCP_RX increase by ~15%

Here are some of the additional raw data with and without threaded napi:
==================================================
udp_rx(Without threaded NAPI)
435.98+-5.16 : Channel 44
439.06+-0.66 : Channel 157

udp_rx(With threaded NAPI)
509.73+-41.03 : Channel 44
549.97+-7.62 : Channel 157
===================================================
udp_tx(Without threaded NAPI)
461.31+-0.69  : Channel 44
461.46+-0.78 : Channel 157

udp_tx(With threaded NAPI)
459.20+-0.77 : Channel 44
459.78+-1.08 : Channel 157
===================================================
tcp_rx(Without threaded NAPI)
472.63+-2.35 : Channel 44
469.29+-6.31 : Channel 157

tcp_rx(With threaded NAPI)
498.49+-2.44 : Channel 44
541.14+-40.65 : Channel 157
===================================================
tcp_tx(Without threaded NAPI)
317.34+-2.37 : Channel 44
317.01+-2.56 : Channel 157

tcp_tx(With threaded NAPI)
371.34+-2.36 : Channel 44
376.95+-9.40 : Channel 157
===================================================

Tested-on: WCN3990 hw1.0 SNOC WLAN.HL.3.2.2-00696-QCAHLSWMTPL-1
Signed-off-by: Abhishek Kumar <kuabhs@chromium.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230203000116.v2.1.I5bb9c164a2d2025655dee810b983e01ecd81c14e@changeid

drivers/net/wireless/ath/ath10k/snoc.c

@@ -927,6 +927,7 @@ static int ath10k_snoc_hif_start(struct ath10k *ar)
 
 	bitmap_clear(ar_snoc->pending_ce_irqs, 0, CE_COUNT_MAX);
 
+	dev_set_threaded(&ar->napi_dev, true);
 	ath10k_core_napi_enable(ar);
 	ath10k_snoc_irq_enable(ar);
 	ath10k_snoc_rx_post(ar);