Add sign-off for some older commits which are missing it.

This sign-off applies to:

c258a0fa6537c00b55b45363e96f979472148137
7bdbc452752bcddc04e957e342c961196208900e
bfa03e3bc9e05515cb50b76111815d3cecb27480

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>