UPSTREAM: nvmem: add support for cell info

Add new structs and routines allowing users to define nvmem cells from
machine code. This global list of entries is parsed when a provider
is registered and cells are associated with the relevant nvmem_device
struct.

A possible improvement for the future is to allow users to register
cell tables after the nvmem provider has been registered by updating
the cell list at each call to nvmem_(add|del)_cell_table().

Bug: 154188491
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit b985f4cba6dbb3b60ad119c6f7e5cbad6f0d7e45)
Signed-off-by: Will McVicker <willmcvicker@google.com>
[willmcvicker: fix trivial merge conflicts]
Change-Id: I4070c4c5d12aa9f555e55ec1f5edccee6395ca7b