Add support for DSBT ELF to ld.so

Add support for DSBT ELF to ld.so

This adds support for DSBT ELF to ld.so.  This uses loadmaps like FD-PIC.
Some code is added in ld.so to initialize the DSBT tables, and there's
also a new target macro FINISH_BOOTSTRAP_RELOC.

Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Aurelien Jacquiot <a-jacquiot@ti.com>
Signed-off-by: Bernd Schmidt <bernds@codesourcery.com>