package/uboot-tools: fix dumpimage for FIT image

The upstream commit 7a01882eb37e7504e2450f474d0cc8db60ed26c2
("common: Kconfig.boot: Add FIT_PRINT config option") introduce
CONFIG_FIT_PRINT and make fit_print_contents() empty if it was
not enabled.

Adding CONFIG_FIT_PRINT=y to UBOOT_TOOLS_MAKE_OPTS does not help
while CONFIG_FIT_PRINT=y affects Makefiles only, not C sources.

Add "#define CONFIG_FIT_PRINT 1" to autoconf.h if FIT_SUPPORT enabled.

It would be better to convert uboot-tools to kconfig infrastructure so
we can use KCONFIG_ENABLE_OPT etc. However, that's a much bigger change
and not suitable for backporting to stable branches. Therefore, for now,
take the simple approach of updating autoconf.h.

Signed-off-by: Atsushi Nemoto <atsushi.nemoto@sord.co.jp>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>