Update handling of soft reset

Change-Id: Ia22b2934b4c85e3c480931c8b92608365351a877
diff --git a/include/ethosu_device.h b/include/ethosu_device.h
index dd34201..eff9054 100644
--- a/include/ethosu_device.h
+++ b/include/ethosu_device.h
@@ -55,7 +55,7 @@
 struct ethosu_device
 {
     volatile uint32_t *base_address;
-    uint32_t reset;
+    uint32_t proto;
     uint32_t pmcr;
     uint32_t pmccntr[2];
     uint32_t pmcnten;