of: property: Provide missing member description and remove excess param

Fixes the following W=1 kernel build warning(s):

 drivers/of/property.c:1239: warning: Function parameter or member 'optional' not described in 'supplier_bindings'
 drivers/of/property.c:1366: warning: Excess function parameter 'dev' description in 'of_link_property'

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: devicetree@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210318104036.3175910-6-lee.jones@linaro.org