OMAP3: overo: Move ethernet CS4 configuration to execute based on board id

By moving the CS4 configuration into the board specific configuration, it
is left free for custom carrier boards. The USRP-E1XX series uses
CS4 to control access to an FPGA, so without this patch the device driver
cannot claim CS4.

Signed-off-by: Philip Balister <philip@opensdr.com>
Tested-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>