tune usb irq (dwc3) based on usb function

This among other things greatly increases tethering performance.

Bug: 202103325
Test: tput improved
(synced from commit f9e02b98b8243d2db566df16d4e763250ac9efaf)

Change-Id: I19b22d748352eb04bc27d85c0f69fa2571b63d53

set_usb_irq.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+# Switch into /proc/irq/$IRQ for the dwc3 usb controller
+cd /proc/irq/*/dwc3/.. || exit 7
+
+# Move the USB Controller (DWC3) interrupt as requested
+# Modem and DIT are on 0/2/5 depending on throughput, so avoid those.
+# 0-3 small, 4-5 medium, 6-7 big
+case "$1" in
+  medium) core=4;;
+  big) core=6;;
+  *) core=0;;
+esac
+
+# This can sometimes fail due to smp_affinity_list no longer existing...
+echo "${core}" > smp_affinity_list