Makefile: drop "tools-only" from no-dot-config-targets

With the introduction of CONFIG_LOCALVERSION support we cannot build
tools without having a config file (as we won't know our PLAIN_VERSION
until then).

Reported-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Tom Rini <trini@ti.com>

Makefile

@@ -411,7 +411,7 @@ timestamp_h := include/generated/timestamp_autogenerated.h
 
 no-dot-config-targets := clean clobber mrproper distclean \
 			 help %docs check% coccicheck \
-			 ubootversion backup tools-only
+			 ubootversion backup
 
 config-targets := 0
 mixed-targets  := 0