net: ethernet: ti: cpsw_new: enable mac_managed_pm to fix mdio resume warning

The commit 744d23c7 ("net: phy: Warn about incorrect mdio_bus_phy_resume()
state") introduced a WARN when phy state is not in the states: PHY_HALTED,
PHY_READY and PHY_UP. When cpsw_new resumes, there have port in PHY_NOLINK
state, so the below warning comes out. Set mac_managed_pm be true to tell
mdio that the phy resume/suspend is managed by the mac, to fix the following
warning:

WARNING: CPU: 0 PID: 965 at drivers/net/phy/phy_device.c:326 mdio_bus_phy_resume+0x140/0x144
CPU: 0 PID: 965 Comm: sh Tainted: G           O       6.1.66-rt18-yocto-preempt-rt #1
Hardware name: Generic AM33XX (Flattened Device Tree)
 unwind_backtrace from show_stack+0x18/0x1c
 show_stack from dump_stack_lvl+0x24/0x2c
 dump_stack_lvl from __warn+0x84/0x15c
 __warn from warn_slowpath_fmt+0x1a8/0x1c8
 warn_slowpath_fmt from mdio_bus_phy_resume+0x140/0x144
 mdio_bus_phy_resume from dpm_run_callback+0x3c/0x140
 dpm_run_callback from device_resume+0xb8/0x2b8
 device_resume from dpm_resume+0x144/0x314
 dpm_resume from dpm_resume_end+0x14/0x20
 dpm_resume_end from suspend_devices_and_enter+0xd0/0x924
 suspend_devices_and_enter from pm_suspend+0x2e0/0x33c
 pm_suspend from state_store+0x74/0xd0
 state_store from kernfs_fop_write_iter+0x104/0x1ec
 kernfs_fop_write_iter from vfs_write+0x1b8/0x358
 vfs_write from ksys_write+0x78/0xf8
 ksys_write from ret_fast_syscall+0x0/0x54
Exception stack(0xe094dfa8 to 0xe094dff0)
dfa0:                   00000004 005c3fb8 00000001 005c3fb8 00000004 00000001
dfc0: 00000004 005c3fb8 b6f6bba0 00000004 00000004 0059edb8 00000000 00000000
dfe0: 00000004 bed918f0 b6f09bd3 b6e89a66

Signed-off-by: Xulin Sun <xulin.sun@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>