rocker: replace fixed stack allocation with dynamic allocation

In hast to fix some sparse warning, I hard-coded a fix-sized array on the stack
which is probably too big for kernel standards.  Fix this by converting array
to dynamic allocation.

Signed-off-by: Scott Feldman <sfeldma@gmail.com>
Acked-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>