mtd: spi-nor: Add support for Infineon s25fs256t

Infineon S25FS256T is 256Mbit Quad SPI NOR flash. The key features and
differences comparing to other Spansion/Cypress flash familes are:
  - 4-byte address mode by factory default
  - Quad mode is enabled by factory default
  - Supports mixture of 128KB and 64KB sectors by OTP configuration
    (this patch supports uniform 128KB only)

Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index 605cdde..2861b73 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -141,6 +141,7 @@
 #define SPINOR_REG_ADDR_STR1V	0x00800000
 #define SPINOR_REG_ADDR_CFR1V	0x00800002
 #define SPINOR_REG_ADDR_CFR3V	0x00800004
+#define SPINOR_REG_ADDR_ARCFN	0x00000006
 #define CFR3V_UNHYSA		BIT(3)	/* Uniform sectors or not */
 #define CFR3V_PGMBUF		BIT(4)	/* Program buffer size */