zephyr: cleanup flash driver name

The flash driver name was changed upstream during the v1.11
development cycle. Remove a shim which kept the old name around in the
Zephyr port now that v1.11 is out.

Signed-off-by: Marti Bolivar <marti@opensourcefoundries.com>
diff --git a/boot/zephyr/include/target.h b/boot/zephyr/include/target.h
index a2c5cf4..00251df 100644
--- a/boot/zephyr/include/target.h
+++ b/boot/zephyr/include/target.h
@@ -31,19 +31,9 @@
 #endif /* !defined(MCUBOOT_TARGET_CONFIG) */
 
 /*
- * Upstream Zephyr changed the name from FLASH_DRIVER_NAME to
- * FLASH_DEV_NAME.  For now, let's just convert the Zephyr name to the
- * one expected by MCUboot. This can be cleaned up after the upstream
- * Zephyr tree has been released and settled down.
- */
-#if !defined(FLASH_DRIVER_NAME) && defined(FLASH_DEV_NAME)
-#define FLASH_DRIVER_NAME FLASH_DEV_NAME
-#endif
-
-/*
  * Sanity check the target support.
  */
-#if !defined(FLASH_DRIVER_NAME) || \
+#if !defined(FLASH_DEV_NAME) || \
     !defined(FLASH_ALIGN) ||                  \
     !defined(FLASH_AREA_IMAGE_0_OFFSET) || \
     !defined(FLASH_AREA_IMAGE_0_SIZE) || \