devres: introduce API "devm_kstrdup"

This patch introduces "devm_kstrdup" API so that the
device's driver can allocate memory and copy string.

Change-Id: Iaeeeb289dc599ae3aa4477386edf9f6b70f83704
Signed-off-by: Manish Badarkhe <badarkhe.manish@gmail.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Git-commit: e31108cad3deabb1a63111d7aa699ca67753c01f
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>