mtd: spi-nor-ids: Add support for XMC XM25QH64C

This chip has been (briefly) tested on the MediaTek MT7688 based GARDENA
smart gateway.

Datasheet: http://xmcwh.com/Uploads/2020-12-17/XM25QH64C_Ver1.1.pdf


Signed-off-by: Reto Schneider <reto.schneider@husqvarnagroup.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>