sh_eth: uninline TSU register accessors

We have uninlined the sh_eth_{read|write}() functions introduced in the
commit 4a55530f ("net: sh_eth: modify the definitions of register").
Now remove *inline* from sh_eth_tsu_{read|write}() as  well and move
these functions from the header to the driver itself. This saves 684
more bytes of object code (ARM gcc 4.8.5)...

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