uboot-tools: fix conditional build of FIT support

uboot-tools: fix conditional build of FIT support

The removal of the unconditional compilation and linking of some .o files were
missed when porting the patch 0003 to the version 2016.07, leading to errors
like these when FIT support is enabled:

tools/fit_common.o: In function `fit_verify_header':
fit_common.c:(.text+0x0): multiple definition of `fit_verify_header'
tools/fit_common.o:fit_common.c:(.text+0x0): first defined here
tools/fit_common.o: In function `fit_check_image_types':
fit_common.c:(.text+0x10): multiple definition of `fit_check_image_types'

When FIT support is disabled, the build does not fail but it includes FIT
support.

Fix the patch 0003 to be equivalent to the original one.

Fixes:
http://autobuild.buildroot.net/results/7494a5b22e3df1c05cdcc47670deaf54d9e04133
http://autobuild.buildroot.net/results/f98f30bbf9d4cdde37a96b9310873d83dd649c54

Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Reported-by: Masahiro Yamada <yamada.masahiro@socionext.com>
CC: Fabio Estevam <festevam@gmail.com>
CC: Carlos Santos <casantos@datacom.ind.br>
Tested-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>