usb: phy: introduce usb_phy device type with its own uevent handler

The USB charger type and status was already propagated to userspace
through kobject_uevent_env during charger notify work. Nevertheless the
uevent could be lost e.g. because it could be fired at an early kernel
boot stage, way before udev daemon or any other user-space app was able
to catch it. Registering uevent hook for introduced usb_phy_dev_type
will allow to query sysfs 'uevent' file to restore that information at
any time.

Reviewed-by: Peter Chen <peter.chen@kernel.org>
Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
Link: https://lore.kernel.org/r/20210531122222.453628-1-grzegorz.jaszczyk@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>