reset: Get the RESET by index without device

Getting a RESET by index with device is not straight forward
for some use-cases like handling clock operations for child
node in parent driver. So we need to process the child node
in parent probe via ofnode and process RESET operation for child
without udevice but with ofnode.

So add reset_get_by_index_nodev() and move the common code
in reset_get_by_index_tail() to use for reset_get_by_index()

Cc: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Simon Glass <sjg@chromium.org>