XMC flash support - WIP (#6725)

* Move the spi vendor list from Esp.h to its own header in eboot.

* Fix ifdef issue with spi_vendors.h

* Add initFlashQuirks() for any chip specific flash initialization.

Called from user_init().

* namespace experimental for initFlashQuirks()

* Slow down flash access during eboot firmware copy

Part 1 - still some work to do

* Slow down flash access during eboot firmware copy on XMC chips

Part 2 - Identify the chip type.

Note: there may still be issues with the access speed change.
This is very much experimental.

* Commit eboot.elf

Co-authored-by: Develo <deveyes@gmail.com>
Co-authored-by: Earle F. Philhower, III <earlephilhower@yahoo.com>

cores/esp8266/flash_quirks.h

@@ -0,0 +1,42 @@
+/*
+ flash_quirks.h
+ Copyright (c) 2019 Mike Nix. All rights reserved.
+ This file is part of the esp8266 core for Arduino environment.
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#ifndef FLASH_QUIRKS_H
+#define FLASH_QUIRKS_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "spi_vendors.h"
+#include "spi_flash_defs.h"
+
+namespace experimental {
+
+void initFlashQuirks();
+
+} // namespace experimental
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif // FLASH_QUIRKS_H