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/boot/bootutil/src/caps.c b/boot/bootutil/src/caps.c
index 85bd6fd..43e1bf6 100644
--- a/boot/bootutil/src/caps.c
+++ b/boot/bootutil/src/caps.c
@@ -41,8 +41,8 @@
 #if defined(MCUBOOT_ENCRYPT_KW)
 	res |= BOOTUTIL_CAP_ENC_KW;
 #endif
-#if defined(MCUBOOT_VALIDATE_SLOT0)
-	res |= BOOTUTIL_CAP_VALIDATE_SLOT0;
+#if defined(MCUBOOT_VALIDATE_PRIMARY_SLOT)
+	res |= BOOTUTIL_CAP_VALIDATE_PRIMARY_SLOT;
 #endif
 
         return res;