docs(fconf): update device tree binding for FCONF

Added a description for the newly introduced 'ns-load-address' property
in the dtb-registry node of FCONF.

Change-Id: Ief8e8a55a6363fd42b23491d000b097b0c48453b
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
1 file changed