dm9000: report the correct LPA

Report the LPA by checking mii_if_info, instead of just saying "no LPA" every
time.

Cc: David S. Miller <davem@davemloft.net>
Cc: Jingoo Han <jg1.han@samsung.com>
Cc: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>