net: ethernet: et131x: Remove redundant register read

Following the removal of an unused variable assignment (remove
unused variable 'pm_csr') the associated register read can also go,
as the read also occurs in the subsequent et1310_in_phy_coma()
call.

Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>