sh_eth: rename PSR bits

In all the SoC manuals (except R-Car gen2) the PHY status register's name
is abbreviated to  PSR with the only valid bit 0 named LMON.  Follow the
suit and rename the corresponding *enum* tag/entry.

Signed-off-by: Sergey Shtylyov <s.shtylyov@omprussia.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>