devres: introduce API "devm_kmemdup

Introduce devm_kmemdup, which uses resource managed kmalloc.
There are several request from maintainers to add this instead
of using kmemdup.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>