flashchips: Add STM M28F256

Very simple 5V, 12V Vpp, 256kbit parallel flash.

Datasheet used:
https://www.mouser.com/catalog/specsheets/STMicroelectronics_M28F256.pdf

Change-Id: I95a59d0b36a9a99e102788bd9c850bf12192efba
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/522
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/include/flashchips.h b/include/flashchips.h
index dd641d9..c1336cd 100644
--- a/include/flashchips.h
+++ b/include/flashchips.h
@@ -904,6 +904,7 @@
 #define ST_M29W010B		0x23
 #define ST_M29W040B		0xE3
 #define ST_M29W512B		0x27
+#define ST_M28F256		0xA8
 #define ST_M28W160ECB		0x88CF
 #define ST_M28W160ECT		0x88CE
 #define ST_M28W320FCB		0x88BB