nvmem: meson-efuse: bindings: Add secure-monitor phandle

Add a new property to link the nvmem driver to the secure-monitor. The
nvmem driver needs to access the secure-monitor to be able to access the
fuses.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>