Add ethosu_deinit()

Added ethosu_deinit method which calls ethosu_deregister_driver().

Change-Id: I12cb1b07169c06c011a80f66d26451431db3948a
diff --git a/src/ethosu_driver.c b/src/ethosu_driver.c
index 84488e5..2be18af 100644
--- a/src/ethosu_driver.c
+++ b/src/ethosu_driver.c
@@ -696,6 +696,11 @@
     return return_code;
 }
 
+void ethosu_deinit(struct ethosu_driver *drv)
+{
+    ethosu_deregister_driver(drv);
+}
+
 void ethosu_get_driver_version(struct ethosu_driver_version *ver)
 {
     assert(ver != NULL);