of/platform: Fix fn definitons for of_link_is_valid() and of_link_property()

of/platform: Fix fn definitons for of_link_is_valid() and of_link_property()

of_link_is_valid() can be static since it's not used anywhere else.

of_link_property() return type should have been int instead of bool.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20190806192654.138605-1-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>