drivers/spi/spi_flash: add flash region protection to controller

Provide a spi controller specific protection callback to take
advantage of special spi flash controllers that have internal
protection registers built into the implementation. It's an
optional callback for spi controllers.

BUG=b:69614064

Change-Id: Ie50a6ce3bbda32620a25dd26fda1af944940bf28
Signed-off-by: Aaron Durbn <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/22879
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/include/spi_flash.h

@@ -120,4 +120,9 @@ int chipset_volatile_group_end(const struct spi_flash *flash);
  * if CONFIG_BOOT_DEVICE_SPI_FLASH is enabled. */
 const struct spi_flash *boot_device_spi_flash(void);
 
+/* Protect a region of spi flash using its controller, if available. Returns
+ * < 0 on error, else 0 on success. */
+int spi_flash_ctrlr_protect_region(const struct spi_flash *flash,
+					const struct region *region);
+
 #endif /* _SPI_FLASH_H_ */