Replace flash partitioning terminology

This change replaces the slot 0/1 terminology with primary/secondary
slot and replaces FLASH_AREA_IMAGE_0/1 with
FLASH_AREA_IMAGE_PRIMARY/SECONDARY. This naming convention may be more
understandable, fits better to MCUs with multiple images and it is an
architecture agnostic alternative as well.

Change-Id: I655a585f6ae023852c671ee6635399efe25209c9
Signed-off-by: David Vincze <david.vincze@arm.com>
Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/samples/mcuboot_config/mcuboot_config.template.h b/samples/mcuboot_config/mcuboot_config.template.h
index 3dee47e..d29f4f6 100644
--- a/samples/mcuboot_config/mcuboot_config.template.h
+++ b/samples/mcuboot_config/mcuboot_config.template.h
@@ -45,7 +45,7 @@
 /* #define MCUBOOT_OVERWRITE_ONLY */
 
 #ifdef MCUBOOT_OVERWRITE_ONLY
-/* Uncomment to only erase and overwrite those slot 0 sectors needed
+/* Uncomment to only erase and overwrite those primary slot sectors needed
  * to install the new image, rather than the entire image slot. */
 /* #define MCUBOOT_OVERWRITE_ONLY_FAST */
 #endif
@@ -64,11 +64,11 @@
 /* #define MCUBOOT_USE_TINYCRYPT */
 
 /*
- * Always check the signature of the image in slot 0 before booting,
+ * Always check the signature of the image in the primary slot before booting,
  * even if no upgrade was performed. This is recommended if the boot
  * time penalty is acceptable.
  */
-#define MCUBOOT_VALIDATE_SLOT0
+#define MCUBOOT_VALIDATE_PRIMARY_SLOT
 
 /*
  * Flash abstraction