Migrate to error constants in glacier

zion/debug/debug.h

@@ -8,14 +8,6 @@ void dbg(const char* fmt, ...);
 void dbgln(const char* str, ...);
 void panic(const char* str, ...);
 
-#define RET_ERR(expr)        \
-  {                          \
-    z_err_t _tmp_err = expr; \
-    if (_tmp_err != Z_OK) {  \
-      return _tmp_err;       \
-    }                        \
-  }
-
 #define UNREACHABLE                                \
   panic("Unreachable %s, %s", __FILE__, __LINE__); \
   __builtin_unreachable();