uboot-imx

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>