greybus: fw-management: Add firmware-management protocol driver

This patch adds Firmware Management Protocol support to firmware core,
which allows the AP to manage firmware on an Interface.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Jun Li <li_jun@projectara.com>
Tested-by: Karthik Ravi Shankar <karthikrs@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>