of: net: export of_get_mac_address_nvmem()

Export

	of_get_mac_addr_nvmem()

and rename it to

	of_get_mac_address_nvmem()

in order to fit the convention followed by the existing exported helpers
of the same kind.

This way, OF compatible drivers using eg. fwnode_get_mac_address() can
do a direct call to it instead of calling of_get_mac_address() just for
the nvmem step, avoiding to repeat an expensive DT lookup which has
already been done once.

Eventually, fwnode_get_mac_address() should probably be updated to
perform the nvmem lookup directly, but as of today, nvmem cells seem not
to be supported by ACPI yet which would defeat this kind of extension.

Suggested-by: Marcin Wojtas <mw@semihalf.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>