peripheral.c: initialize common members only

Other members will be initialized according to peripheral configuration.

src/peripheral/src/peripheral.c

@@ -43,7 +43,7 @@ void peripheral_update(union peripheral *const p)
 void peripheral_init(const struct peripheral_cfg *const cfg,
     union peripheral *const p)
 {
-    *p = (const union peripheral){0};
+    p->common = (const struct peripheral_common){0};
 
     switch (p->common.type = cfg->type)
     {