iplink: hsr: add support for creating PRP device similar to HSR

iplink: hsr: add support for creating PRP device similar to HSR

This patch enhances the iplink command to add a proto parameters to
create PRP device/interface similar to HSR. Both protocols are
quite similar and requires a pair of Ethernet interfaces. So re-use
the existing HSR iplink command to create PRP device/interface as
well. Use proto parameter to differentiate the two protocols.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>