net: sh_eth: rename name structures as rcar_gen[12]_*

Rename structures describing R-Car SoCs as rcar_gen[12]_*
rather than r8a77[79]x_*. This seems a little easier on the
eyes. And will make things slightly cleaner in a follow-up
patch that adds fallback-compatibility strings for these SoCs.

Note that R-Car Gen2 and RZ/G1 have many compatible IP blocks.  The
approach that has been consistently taken for other IP blocks is to name
common code, compatibility strings and so on after R-Car Gen2.

Also rename sh_eth_set_rate_r8a777x as sh_eth_set_rate_rcar as
it it is used by the R-Car generations supported by the driver.

This patch should have no run-time effect and
is compile-tested only.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>