spi25_statusreg: support reading/writing configuration register

One more variation of registers.

This one is read via a separate RDCR command, but written as if it's
SR2 using WRSR_EXT2.

Ported to flashprog w/o the FEATURE_CFGR flag, we'll already have that
information in the register description.

Change-Id: I45f9afcc31f1928ef6263a749596380082963de4
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Orignal-Reviewed-on: https://review.coreboot.org/c/flashrom/+/66211
Orignal-Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Orignal-Reviewed-by: Nikolai Artemiev <nartemiev@google.com>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/71007
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/include/spi.h b/include/spi.h
index 9e655fc..8935997 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -171,6 +171,11 @@
 #define JEDEC_WRSCUR_OUTSIZE	0x01
 #define JEDEC_WRSCUR_INSIZE	0x00
 
+/* Read Configuration Register */
+#define JEDEC_RDCR		0x15
+#define JEDEC_RDCR_OUTSIZE	0x01
+#define JEDEC_RDCR_INSIZE	0x01
+
 /* Enter 4-byte Address Mode */
 #define JEDEC_ENTER_4_BYTE_ADDR_MODE	0xB7