nvmem: meson-efuse: remove econfig global

Having a global structure holding a reference to the device
structure is not very nice. Allocate the econfig instead and fill
the nvmem information as before

Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>