drivers/core: use memdup() instead of malloc()+memcpy()

drivers/core: use memdup() instead of malloc()+memcpy()

Use memdup() instead of open-coding it.

In the dm_setup_inst() case, there was never any reason to use
calloc(), as the whole allocation is definitely initialized via the
immediately following memcpy().

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>