mtd: spi-nor: support GigaDevice gd25lq64c

Also note the GigaDevice JEDEC ID.

No write-protect support yet, since this flash uses a different status
register layout.

Cc: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Acked-by: Marek Vasut <marex@denx.de>