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/scripts/flash.sh b/scripts/flash.sh
index 7353dd7..a2c58c7 100755
--- a/scripts/flash.sh
+++ b/scripts/flash.sh
@@ -8,8 +8,8 @@
 h
 r
 loadfile outdir/$BOARD/zephyr.bin $BASE_BOOT
-loadfile hello.signed.bin $BASE_SLOT0
-loadfile shell.signed.bin $BASE_SLOT1
+loadfile hello.signed.bin $BASE_PRIMARY_SLOT
+loadfile shell.signed.bin $BASE_SECONDARY_SLOT
 q
 EOF