sh_eth: WARN_ON() access to unimplemented TSU register

Commit 3365711d ("sh_eth: WARN on access to a register not implemented
in a particular chip") added  WARN_ON() to sh_eth_{read|write}() but not
to sh_eth_tsu_{read|write}(). Now that we've routed almost all TSU register
accesses  (except TSU_ADR{H|L}<n> -- which are special) thru the latter
pair of accessors, it makes sense to check for the unimplemented TSU
registers as well...

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