mtd: spi: Convert is_locked callback to is_unlocked

There was no user of this callback after 5b66fdb29dc3 anymore, and its
semantic as now inconsistent between stm and sst26. What we need for the
upcoming new usecase is a "completely unlocked" semantic. So consolidate
over this.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index ba98ad4..2595bad 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -517,8 +517,8 @@
  *			spi-nor will send the erase opcode via write_reg()
  * @flash_lock:		[FLASH-SPECIFIC] lock a region of the SPI NOR
  * @flash_unlock:	[FLASH-SPECIFIC] unlock a region of the SPI NOR
- * @flash_is_locked:	[FLASH-SPECIFIC] check if a region of the SPI NOR is
- *			completely locked
+ * @flash_is_unlocked:	[FLASH-SPECIFIC] check if a region of the SPI NOR is
+ *			completely unlocked
  * @quad_enable:	[FLASH-SPECIFIC] enables SPI NOR quad mode
  * @octal_dtr_enable:	[FLASH-SPECIFIC] enables SPI NOR octal DTR mode.
  * @ready:		[FLASH-SPECIFIC] check if the flash is ready
@@ -567,7 +567,7 @@
 
 	int (*flash_lock)(struct spi_nor *nor, loff_t ofs, uint64_t len);
 	int (*flash_unlock)(struct spi_nor *nor, loff_t ofs, uint64_t len);
-	int (*flash_is_locked)(struct spi_nor *nor, loff_t ofs, uint64_t len);
+	int (*flash_is_unlocked)(struct spi_nor *nor, loff_t ofs, uint64_t len);
 	int (*quad_enable)(struct spi_nor *nor);
 	int (*octal_dtr_enable)(struct spi_nor *nor);
 	int (*ready)(struct spi_nor *nor);