marvell: phy-mvebu-cp110-comphy: Add power ON support for 2500BASET mode

commit  259a9f2cf1aa05806c69c2808ccca68c83034ee1 from
https://git.assembla.com/cavium/WindRiver.linux.git

Add PHY_INTERFACE_MODE_2500BASET to mvebu_comphy_power_on callback.

Change-Id: I305f1ae4e74765bdebc78b4385998775509477f4
Signed-off-by: Stefan Chulski <stefanc@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/52606
Tested-by: sa_ip-sw-jenkins <sa_ip-sw-jenkins@marvell.com>
(cherry picked from commit 4430734cbc05e576e1bc5a0c37cedfc89d736997)
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/52707
Signed-off-by: Meng Li <Meng.Li@windriver.com>
Signed-off-by: Ruiqiang Hao <Ruiqiang.Hao@windriver.com>