Documentation: nvmem: add nvmem api level and how-to doc
Documentation: nvmem: add nvmem api level and how-to doc

This patch add basic how-to and api summary documentation for simple
NVMEM framework.

Signed-off-by: Srinivas Kandagatla <e9a3fcd7365f8e6a430ada3b68b984cb4aaf0c3e@linaro.org>
Tested-by: Philipp Zabel <db7328bbf81a38b011e8d0f5302fd54c788d0608@pengutronix.de>
Tested-by: Rajendra Nayak <4802c9324e296bd4f067f90ad87878b5665d33d2@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <4645f7897fd33786a2ee1264d590b3c400559d85@linuxfoundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs