net/ps3_gelic_net: Add gelic_descr structures

In an effort to make the PS3 gelic driver easier to maintain, create two
new structures, struct gelic_hw_regs and struct gelic_chain_link, and
replace the corresponding members of struct gelic_descr with the new
structures.

The new struct gelic_hw_regs holds the register variables used by the
gelic hardware device.  The new struct gelic_chain_link holds variables
used to manage the driver's linked list of gelic descr structures.

Signed-off-by: Geoff Levand <geoff@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>