net: sh_eth: add SH_ETH_TYPE_ condition

net: sh_eth: add SH_ETH_TYPE_ condition

At the moment, the driver supports the following CPUs:
 - GETHER (Gigabit Ethernet) : SH7763, SH7734
 - ETHER  (Fast Ethernet)    : SH7724, SH7757

And the driver had the following "#if":

 #if defined(CONFIG_CPU_SH7763) || defined(CONFIG_CPU_SH7734)
 #if !defined(CONFIG_CPU_SH7757) && !defined(CONFIG_CPU_SH7724)
 - Those are for GETHER

 #if defined(CONFIG_CPU_SH7724) || defined(CONFIG_CPU_SH7757)
 - This is for ETHER

So, for clean up the code, this patch adds SH_ETH_TYPE_GETHER and
SH_ETH_TYPE_ETHER. And then, the patch modifies the above "#if".

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>