dm: event: add EVT_DM_POST_INIT_R event type

This patch introduces EVT_DM_POST_INIT_R event type for handling hooks
after relocation.

Fixes: 55171aed ("dm: Emit the arch_cpu_init_dm() even only before relocation")
Suggested-by: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Tested-by: Milan P. Stanić <mps@arvanta.net>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Roland Ruckerbauer <mail@ruabmbua.dev>
Tested-by: Roland Ruckerbauer <mail@ruabmbua.dev>
Fixed missing event name in event.c:
Signed-off-by: Simon Glass <sjg@chromium.org>