tools: refactor HOSTLOADLIBES_* options

The tools mkimage, dumpimage, fit_info, fit_check_sign
always have the common libraries to be linked,
so HOSTLOADLIBES_* can be consolidated a little bit.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Simon Glass <sjg@chromium.org>
Series-to: uboot
Series-prefix: RESEND
Commit-notes:
  - Resend as a single patch with Simon's Acked tag.
END
kbuild,tools: generate wrapper C sources automatically by Makefile

There are many source files shared between U-boot image and tools.
Instead of adding a lot of dummy wrapper files that just include
the corresponding file in lib/ or common/ directory,
Makefile should automatically generate them.

The original inspiration for this came from
scripts/Makefile.asm-generic of Linux Kernel.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Series-to: uboot
Series-cc: sjg
Series-cc: Charles Manning <cdhmanning@gmail.com>
Series-cc: Gerhard Sittig <gsi@denx.de>