phy: omap-usb2: support suspend/resume

phy: omap-usb2: support suspend/resume

Relying on PM-ops for shutting down PHY clocks was a
bad idea since the users (e.g. USB DWC3) might not
have been suspended by then.

Get rid of all PM-ops. It is the sole responsibility
of the PHY user to properly turn OFF and de-initialize
the PHY as part of its suspend routine.

Enable/disable PHY clock as part of ->init()/->exit()
call respectively. With this phy_init() and phy_exit()
can be called by PHY user during suspend/resume.

This is similar to what is done for ti-pipe3 driver.
See 31c8954efb1b ("phy: ti-pipe3: fix suspend")

The pm_runtime_enable() call in omap_usb2_probe()
is still required because without it, phy_create()
will not enable runtime PM on the phy device it
creates and phy_init() will not call
pm_runtime_get_sync().

Without pm_runtime_get_sync(), ocp2scp hwmod will
_not_ enable the IP and, thus, we will have abort
exceptions.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>