dm: Add support for all targets which requires MANUAL_RELOC

Targets with CONFIG_NEEDS_MANUAL_RELOC do not use REL/RELA
relocation (mostly only GOT) where functions aray are not
updated. This patch is fixing function pointers for DM core
and serial-uclass to ensure that relocated functions are called.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Simon Glass <sjg@chromium.org>