usb: phy: ab8500-usb: fix last notifier arguments

Fix last ab->phy.notifier call to use vbus_draw as notifier argument, as
that's used in ab8500_charger to control charging current.

Also drop a related TODO comment, and the additional
ux500_musb_set_vbus(musb, 0), as with this patch it was causing an
erratic behaviour of gadget ep0 state machine.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>