flashchips: Add XMC XM25QU64A

Alas, there is no datasheet to be found. Block erasers are confirmed
by SFDP readings, chip erasers are guessed.  All similar chips (e.g.
EN25S64, XM25QH64A) have four block-protection bits, so we try that.

Change-Id: I705e9eed1fbc9dd97b8235a1887d88bcde7de5e0
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/577
diff --git a/include/flashchips.h b/include/flashchips.h
index 7654c33..bf632af 100644
--- a/include/flashchips.h
+++ b/include/flashchips.h
@@ -864,6 +864,7 @@
 #define ST_M25P32		0x2016
 #define ST_M25P64		0x2017
 #define ST_M25P128		0x2018
+#define XMC_XM25QU64A		0x3817
 #define ST_M45PE10		0x4011
 #define ST_M45PE20		0x4012
 #define ST_M45PE40		0x4013