usb: phy: twl4030-usb: Fix regressions to runtime PM on omaps

usb: phy: twl4030-usb: Fix regressions to runtime PM on omaps

Commit 30a70b026b4cd ("usb: musb: fix obex in g_nokia.ko causing kernel
panic") attempted to fix runtime PM handling for PHYs that are on the
I2C bus. Commit 3063a12be2b0 ("usb: musb: fix PHY power on/off") then
changed things around to enable of PHYs that rely on runtime PM.

These changes however broke idling of the PHY and causes at least
100 mW extra power consumption on omaps, which is a lot with
the idle power consumption being below 10 mW range on many devices.

As calling phy_power_on/off from runtime PM calls in the USB
causes complicated issues with I2C connected PHYs, let's just let
the PHY do it's own runtime PM as needed. This leaves out the
dependency between PHYs and USB controller drivers for runtime
PM.

Let's fix the regression for twl4030-usb by adding minimal runtime
PM support. This allows idling the PHY on disconnect.

Note that we are changing to use standard runtime PM handling
for twl4030_phy_init() as that function just checks the state
and does not initialize the PHY. The PHY won't get initialized
until in twl4030_phy_power_on().

Fixes: 30a70b026b4cd ("usb: musb: fix obex in g_nokia.ko causing kernel panic")
Fixes: 3063a12be2b0 ("usb: musb: fix PHY power on/off")
Cc: stable@vger.kernel.org # v3.15+
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>