Migrate to error constants in glacier

lib/mammoth/include/mammoth/debug.h

@@ -10,11 +10,3 @@ void dbgln(const char* fmt, ...);
 void check(uint64_t);
 
 void crash(const char*, z_err_t);
-
-#define RET_ERR(expr)        \
-  {                          \
-    z_err_t _tmp_err = expr; \
-    if (_tmp_err != Z_OK) {  \
-      return _tmp_err;       \
-    }                        \
-  }