Makefile: use if_change_dep for u-boot.cfg

cmd_cpp_cfg generates a dependency output, but because it's invoked using
if_changed rather than if_changed_dep, that dependency file is ignored.
This results in Kbuild not knowing about which files u-boot.cfg depends
on, so it may not be rebuilt when required.

A practical result of this is that u-boot.cfg may continue to reference
CONFIG_ options that no longer exist in the source tree, and this can
cause the adhoc config options check to fail.

This change modifies Makefile to use if_changed_dep, which in turn causes
all dependencies to be known to the next make invocation.

Signed-off-by: Stephen Warren <swarren@nvidia.com>

Makefile

@@ -937,7 +937,7 @@ u-boot.dis:	u-boot
 		$(OBJDUMP) -d $< > $@
 
 u-boot.cfg:	include/config.h FORCE
-	$(call if_changed,cpp_cfg)
+	$(call if_changed_dep,cpp_cfg)
 
 # Check that this build does not use CONFIG options that we don't know about
 # unless they are in Kconfig. All the existing CONFIG options are whitelisted,

scripts/Makefile.spl

@@ -217,7 +217,7 @@ cmd_cpp_cfg = $(CPP) -Wp,-MD,$(depfile) $(cpp_flags) $(LDPPFLAGS) -ansi \
 	-DDO_DEPS_ONLY -D__ASSEMBLY__ -x assembler-with-cpp -P -dM -E -o $@ $<
 
 $(obj)/$(SPL_BIN).cfg:	include/config.h FORCE
-	$(call if_changed,cpp_cfg)
+	$(call if_changed_dep,cpp_cfg)
 
 pythonpath = PYTHONPATH=tools