tinyconfig: enable CONFIG_LD_DEAD_CODE_DATA_ELIMINATION

This CONFIG option, if supported by the architecture, helps reduce the
size of vmlinux.

For example, the size of vmlinux with ARCH=arm tinyconfig decreases as
follows:

   text	   data	    bss	    dec	    hex	filename
 631684	 104500	  18176	 754360	  b82b8	vmlinux.before
 455316	  93404	  15472	 564192	  89be0	vmlinux.after

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>