drivers: net cpsw: Enable In Band mode in cpsw for 10 mbps

This patch adds support for enabling In Band mode in 10 mbps speed.
RGMII supports 1 Gig and 100 mbps mode for Forced mode of operation.
For 10mbps mode it should be configured to in band mode so that link
status, duplexity and speed are determined from the RGMII input data
stream

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>