Use ALL-y style instead of ifeq blocks for better readability

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
diff --git a/board/pcs440ep/config.mk b/board/pcs440ep/config.mk
index 23631c5..f560ec6 100644
--- a/board/pcs440ep/config.mk
+++ b/board/pcs440ep/config.mk
@@ -26,7 +26,7 @@
 #
 
 # Check the U-Boot Image with a SHA1 checksum
-ALL += $(obj)u-boot.sha1
+ALL-y += $(obj)u-boot.sha1
 
 PLATFORM_CPPFLAGS += -DCONFIG_440=1