sh_eth: kill useless check in __sh_eth_get_regs()

Iff TSU registers exist on a given [G]Ether controller, they always include
the CAM entry table registers (TSU_ADR{H|L}<n>), thus the check for invalid
TSU_ADRH0 offset in __sh_eth_get_regs() is useless...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>