dtc: Don't build tests as part of "all"

Currently "make all" for dtc will build (but not run) the testcase
binaries.  This is a problem for cross compiles, because building the
tests will attempt to run the dumptrees utility on the host system,
which won't work if it's cross-compiled of course.

Although it would be possible to separately build host binaries,
there's not a lot of value in doing so since we don't have a facility
for cross-executing the testsuite anyway.

Therefore, remove the tests from the "all" target.  It will still, of
course, be build as a prerequisite to "make check" which will run the
testsuite.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Makefile

@@ -46,7 +46,7 @@ else
 DEPTARGETS = $(filter-out $(NODEPTARGETS),$(MAKECMDGOALS))
 endif
 
-all: dtc ftdump libfdt tests
+all: dtc ftdump libfdt
 
 install: all
 	@$(VECHO) INSTALL