For testing we need to build some ELF files containing binman symbols. Add
these to the Makefile and check in the binaries:

   u_boot_binman_syms - normal, valid ELF file
   u_boot_binman_syms_bad - missing the __image_copy_start symbol
   u_boot_binman_syms_size - has a binman symbol with an invalid size
Signed-off-by: NSimon Glass <sjg@chromium.org>