mtd: spi-nor: add TB (Top/Bottom) protect support

Some flash support a bit in the status register that inverts protection
so that it applies to the bottom of the flash, not the top. This yields
additions to the protection range table, as noted in the comments.

Because this feature is not universal to all flash that support
lock/unlock, control it via a new flag.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

include/linux/mtd/spi-nor.h

@@ -85,6 +85,7 @@
 #define SR_BP0			BIT(2)	/* Block protect 0 */
 #define SR_BP1			BIT(3)	/* Block protect 1 */
 #define SR_BP2			BIT(4)	/* Block protect 2 */
+#define SR_TB			BIT(5)	/* Top/Bottom protect */
 #define SR_SRWD			BIT(7)	/* SR write protect */
 
 #define SR_QUAD_EN_MX		BIT(6)	/* Macronix Quad I/O */
@@ -116,6 +117,7 @@ enum spi_nor_ops {
 
 enum spi_nor_option_flags {
 	SNOR_F_USE_FSR		= BIT(0),
+	SNOR_F_HAS_SR_TB	= BIT(1),
 };
 
 /**