ext/ffi: make zend_ffi_types static

Author: MaxKellermann

ext/ffi/ffi.c

@@ -5538,7 +5538,7 @@ static const zend_ffi_type zend_ffi_type_long_double = {.kind=ZEND_FFI_TYPE_LONG
 
 static const zend_ffi_type zend_ffi_type_ptr = {.kind=ZEND_FFI_TYPE_POINTER, .size=sizeof(void*), .align=_Alignof(void*), .pointer.type = (zend_ffi_type*)&zend_ffi_type_void};
 
-const struct {
+static const struct {
 	const char *name;
 	const zend_ffi_type *type;
 } zend_ffi_types[] = {